[lvalero]

I am not very familiar with RPM but sounds it is a cool way to approach to AM.

With this system you may as well roll 6d against Form+technique. Another option is to roll 3d against the average of form and technique. With this second alternative the MoS should be Final cost / 20 instead of / 10.

Have you considered to have techniques as skills and have forms as advantages like Magery (ignem)? This way you could roll against technique + form in a very natural way.

By the way, in example you sent I think I would rule that the mage needs to be succesful with both rolls to prevent over-specialization