Flexible Formulaic Magic

Hi all
If I understand without problem how works the virtue (adding or substracting 5 levels to a formulaic spell to change it slightly), something seems unclear when I read the explanation :
To calculate penetration, is it from the known formulaic spell or from the flexible result?

I give an exemple : if I take "sense the nature of the vis" (InVi5 touch, mom, ind) and want to make it InVi10 (touch, conc, ind)... do I calculate the penetration from 5 or from 10?
Tech+Form+sta+aura+dice must be at least (spell+5-10) to be able to use the flexible spell as it is the case for the normal spell (spell-10) ?

Thanks

I've always assumed it's from the "flexible result": if make the effect more powerful, you lose in penetration and viceversa. In other words, it works as if you really knew a different spell with the new parameters.

it makes sense...
so if you can cast the normal spell, but not the flexible spell, you cannot cast it I guess...

I concur, that's how we run it.

You can cast your normal spells, too, the virtue gives just an option.

Doesn't the Virtue description explicitly say that success, penetration, etc are all based on the new [modified] casting level?

No, it is not clear at all, otherwise I wouldn't ask... and both solution have their plus and minus

Upon re-reading it, I don't think it is unclear. At all. It says: "Casting succes....is based on the casting level of the spell" "Casting level" is the actual level of spell you cast, which might be 5 levels higher or lower than the formulaic spell you know (or the same level) because you have changed one parameter up or down (or not).

It also says: "You may raise or lower the spell..." so you can cast it as is if you don't need to change.

This might be a grey area, but we allow FFM to change a parameter within the same step (e.g. from Concentration to Diameter). It still counts as the one parameter you may change, but it doesn't change the spell level, since it is the same step. We feel this is a logical interpretation, although it does not explicitly say so in the description of the virtue.

Perhaps this should be brought to the attention of David Chart for the errata?

It was not clear that the casting level was changing when adding or substracting 5... so that's mean that adding 5 could make it impossible to cast...

In my ArM5 it says: "You may raise or lower the casting level of the spell...", which goes against this interpretation.

It would be impossible to cast. The way I read the above, when you know a formulaic spell you also know all variations described in FFM. It doesn't do anything for casting per se.

an excellent idea

I agree too. There's a similar detail about the "Short-Ranged Magic" flaw:

Even though Eye range is not "greater" than Touch range, it seems reasonable that the penalty should still apply to Lab Totals for effects at Eye range.