Screw it! Though I dont use ply, I tend to go with plastic. ABS is my friend
it can take a hit and still be ok. I've also got some CF sheet that I've had for about 10 years now. I've had ply crack and break on bad landings, plus the tools I have at home, plastic is easier for me to cut.
Though I do end up makeing a lot of custom mounts for various planes. Not the bulk head but the mount that bolts to the motor. Working at a high end car stereo shop we have some metal fabing stuff at work. I grab some of the really small scraps of aluminum and will cut out my own mounts at home ith little more then a small drill press and a dremell.
Heres one I made for a funbat a year ago