Does anyone know of any published spells designed to enhance Parma Magica? Or have you had any by house rules in a saga?
Something like a Range: Reach, Duration: Concentration, Target: Small (or Part) Mu Vi (Te) to make a "facet" of your Parma impermeable against solid missiles? Or D: Sun (R/T as above) Mu Im to make your Parma act as a camouflaging curtain? And etc.
None, as far as I know, and this is likely impossible to achieve without original research, since muto vim typically needs to be used on formulaic spells of some kind, not arcane abilities.
Why not just cast a spell to make your flesh impermeable to normal missiles or give you camouflage? I know it won’t be MuVi and be MuCo or MuIm instead but it seems like a better way to do it to me considering being able to make any spell any other spell with MuVi and no requisites in the relevant arts always seemed kinda strange to me.
Agreed. Hermetic magic has multiple ways of creating effects, but sometimes it's just better to make a straightforward one. You could turn your ideas into a hammer with MuMeTeHe, but it's awfully simpler to just creo a hammer. Same thing with transforming your parma to block non magical things.
Sort of indirectly, but Unravelling the Fabric of (Form) compliments Parma Magica beautifully in this edition:
Thanks for the input, everyone.
I'm basically just brainstorming here. I keep trying to think of a way to duplicate a shield spell as depicted in The Dresden Files without half a dozen requisites. I'm also pretty sure other troupe members are thinking along the same lines at times, so I'm trying to have a few answers ready when they ask a question.
Ah, but we don't use "this edition" we use the previous. No subtracting spell levels from Penetration, so a high level spell with a decent roll has pretty high Pen.
I think an universal protection is not in the paradigm of Ars Magica (each Art protects against itself), but if you want to protect against non-magical projectile, it's quite easy to do with a ReTe/He
Then the above-mentioned trick is ... much less useful, I'll admit.
Ahhh. I was pondering a response when I noticed this. I have no ideas, having not played previous.
It may be useful to mention when you're not using most recent editions, otherwise a lot of the ideas and data you get will be not useful to you. (Though I guess 4th and 5th do have good overlaps)
In that case, why not use ReVi effects instead of Parma to provide Magic Resistance? It's far more effective (which is why it was removed in 5th edition) and you can do all sort of tricks on those that you cannot do on a Parma (particularly because there are far fewer restrictions on metamagic in previous editions).
This thread led me to look up the PeVi spell in Contested Isle that knocks down the target’s Parma. Interestingly, that spell uses the PeVi base effect to negate a “magical effect.” All the other techniques specify “spell” as potential targets, but only Perdo broadens this to allow targeting magical effects the caster has knowledge of.
There’s potential here for a CrVi spell that strengthens your Parma, a spell that sustains your Parma beyond sunrise/sunset, and spells that alter your Parma to, for example, make it work better against a specific form.
All these effects seem within Hermetic Theory using the PeVi effect as a touchstone, but someone would need to invent new guidelines, probably a Minor Breakthrough for each. Seems like a fun character arc or story seed.
Interesting idea, idea to hammer.
I could bury someone with an argument!
Careful. There's a lot of arguments on this board. The last thing we want is someone who thinks dead bodies is the right way to win his/her point. 
Well, in principle you do not need a Breakthrough, even a Minor one, for a new guideline.
One reason I would not want "Hermetic spells strengthening Parma" in my 5th edition games though, is that Parma should "rule" as it is, and in particular it should be as strong as possible for a) Hedge Wizards who join the Order (who already do not get the full benefit in that they do not get to add the Form Bonus) and b) Hermetic magi who are not Vim specialists. I believe b) was actually the main reason why ReVi "Charms agaist Magic" were removed from 5th edition.