Help me out with Chaotic Magic, please

And also Spontaneous magic, to begin with. Maybe I'm not getting it right, haven't read it thoroughly enough, or just plainly remember previous editions better.

When sponting, you look at the level guidelines, decide upon the tech/Form (e.g. Cr Ig), declare an effect (e.g. create light from a small rock, equivalent of a torch, base lvl 3), and Range, Duration, Target (e.g. touch +1 mag, sun +2 mags, individual +0), and calculate a final level (e.g. lvl 10). You roll, calculate and get a final level. Let's say we decide to spend fatigue, so we halve the total, and thus need a total of 20+, for our decided effect to happen.
If you get less that you wish for, nothing happens, if you get more, you get it, and nothing else. Right? This was the simple version, like in 4th ed, where Penetration was Casting Total.

But now things get more tricky, factoring in Penetration. In addition to the above example, you want penetration above 0, so you leave the effect open-ended, getting anything more than the minimum required total as penetration. So anything above the needed level 10 effect - after halving casting total - is penetration. Am I still on the ball?

And what about other open ended effects, are they still allowed? Using the same level as above, supposing I wanted the rock to shed light at minimum equivalent to a torch, or as high as I can get it? Could I do this? In that case, I'd need to specify how much - a fixed amount - to leave for Penetration. Right?
Or alternatively create light qeuivalent to a torch, with x penetration, for as long as possible, leaving Duration open ended (of course, Sun is the cap, since it's improvised).

So in conclusion, you can leave one factor open ended.

But what about Chaotic Magic? It's a Major Flaw, but it seems to me to be a relic from previous editions, made obsolete by the new rules.
When improvising, you do as normal, but if the effect attained varies by more than one level from what's specified, results get beyond your control. When and how does this happen? I can simply always leave Penetration open ended, in which case, only if not reaching the level wished for, does the Chaotic magic kick in. No very high Stress die rolls, with multiple 1's, can result in anything bad. And if I make sure I never improvise where I rely on any contribution from the die, then I'm in the clear. Sure, those chancing it, and calculating they'd probably roll 3+ more often than not, can get slightly higher effects, but the contricution of 1 die - unless it's at least one '1' - is only a full magnitude in the extreme. Perhaps the rounding down can sometimes mean a magnitude higher, but still...

So my question is, has anybody else seen this problem? Any fixes?

What? Nobody has anything to say? That's a shame, this is really something I'd like to discus.

Nothing useful to say, no. I carefully steered people away from that flaw during chargen since not only is the wording a bit wooly, but it's a nightmare to adjudicate things like that on the fly.

I would say that if you have chaotic magic you need to specify the effect and the penetration and cannot leave anything open and then if you miss the rtarget you get problems. But I have never had anyone with this flaw in 3rd, 4th or 5th ed so this is just IMHO

Hmmm. Thinking about it, this seems like a fix. But I'll have to try it out in play. So the real Flaw part of Chaotic Magic is that you need to specify and 'lock' all parameters, including Penetration.
Sure, if you Spont and don't spend Fatigue, dividing by 5 means being off by more than 1 level is unlikely. If you just calculate with an average roll of around 5, only rolling either 0 (not botching) or 10+ (possible on a Stress die) will mean you're more than 1 level off. But spending Fatigue, and dividing by 2 means this is more likely. Also, the Aura can be a variable. It may vary from saga to saga, whether or not the PCs know the local aura. If you don't, Cahtic magic really is risky (but hey, it's a Major Flaw, so...). I usually tell the PCs the aura as being 'low, medium or high', after they've tries casting something, or even using an InVi spell to detect the aura. But once the first Botch, has happened, this is usually pretty obvious. Or if they juuuuust barely make their spell roll, and need to know ehwther the 'medium' aura is +4, +5 or +6. Or if Penetration is an issue. Nevertheless, Players should be adult and mature enough to treat such knowledge as meta, and not let it affect their PC...much.

This way,. Chaotic Magic certainly seems a Major Flaw. It will surely force my Tremere Magus to use Spont magic wisely.

Well, if you aim for a level where you need a 6 on the roll when spending fatigue, you aren't likely to miss. Since you can always spend confidence to help if you are low while getting 16 (to be 5 over what you need) is unlikely (takes 1 1 4+ or 1 8+ or 4% of the time.).

Penetration is your wild card though that you can use to basically adjust the spell level to get to that point.

There is no risk in sponts where you don't use fatigue since you divide casting total 5 (there is no die roll).

No die roll added to casting total if not spending Fatigue? My mind must be clouded by all my years of 4th ed gaming, I did not remember that. So effectively, Chaotic magic never affects weak Spont magic (unless the SG insists upon keeping Aura modifier secret!).

But how is Penetration a wild card? You need to specify in advance what effect, range, duration and target you're Spont'ing after, as well as the desided penetration. Otherwise the flaw has no effect.
So, unlike non-Chaotic Spont, we're now being penalized for rolling consequetive 1's. Since this first off means, the final level of effect surely is off by more than 1 level. And secondly since we decided upon a Penetration of X, and anything over this is lost. Especially since the spell is now out of our control, as per the Flaw description, and propably won't do what we want.

Wild card to get to desired level. If your casting total is +20 and you want to cast a level 5 spot. Based on what I said: Aim for 26 casting total with the dice that with fatigue divides by two for 13 total, So you say 8 penetration (level 5 spell, +8 penetration). If you roll a 0-14 (and not botch), then you end up with spell going off with 5-12 penetration or within 5 (Spell goes off (no chaotic effects).

If your casting total was 18 and you are casting level 10 spell, aim for a 24 (6 on the die) so 2 penetration. The penetration allows you to adjust your target number needed by the roll down to the exact point for the formula I mentioned. Get a 0 on the roll (botch chance), the spell fails. Get a 2-14, spell goes off with 0 to 6 penetration and you are thus safe.

Sure, a 1 followed by 8, 9 or 10 or 1,1 and (4+ or another 1) will hurt but that is rare and why chaotic magic is a flaw. Things not only go wrong but they go wrong with a much higher power than you were aiming for.

IDHMBWM, only a 4th ed pdf, but is Chaotic Magic still defined as "if the spell is off by more than 5 levels..."? I thought 5th ed. ruled it as off by more than 1 level. If this is the case, it is indeed troublesome. Unless you operate at such low leves as not bothering to spend Fatigue.
In this case, the situation is only non-Chaotic if you roll 4-8 (getting Penetration of 7-9)

Hmmmm, I missed that change. This basically gives you a range of 3 numbers (target number and +1/-1 or 6 numbers of the dice when you divide by 2). Penetration still lets you adjust the level of the spell so that you can cast spont spells that are much loser than your casting total. I still say adjust for a 5 or 6 on the die. This means that 4, 5,6, 7, 8, 9, 1-2, 1-3, and 1-4 on the die generally will be good for you.