Yep. It'd cover my 3"x2" arc well !
About the helmet, I think it will open like all the previous helmets, since the MK47 also opens like usual and these two suits seem relatively close. Now how I don't know if the wings do cause a problem or not but if you take a look at this pic (projectearth7's helmet):
It looks like it slides out without too much trouble. If it doesn't, we'll have to figure out a system that pushes the faceplate out, then rotates it on the top of the helmet. The jaw apparently slides out forward, if it's like the MK47.
laelle, didn't you say a few pages back that you had an idea on how to animate the cannon ? Because I had a crazy idea that just might work with some knowledge in arduino programmation, or some help from a guy like therealtonystark :
what if we could link the cannon to an accelerometer in the helmet ? This way, when the cannon is up, it follows your watch : wether you look left right up or down, it reacts accordingly ? That'd be awesome, don't you think ?