Hi Bruce,

Well, since there is a LOT of torque on those stand offs with the outrunner, I had to make the firewall stiff. REALLY stiff.

It's a piece of 1/8" A/C ply bonded to a piece of 1/8" balsa, then laminated on both sides with 2.4 ounce C/F and .2 oz carbon tissue. Vacuum pulled to about 22 in Hg. It's REALLY strong and light.

At the points where the stand offs screw into the firewall, I used a piece of 1/2" tubing to remove a round section of the balsa from the back, careful not to get into the A/C ply. Then I installed small flush discs of hardwood dowel, and drilled...voila. Sounds much more complicated than it is but it works great. I don't think I've ever seen Emory's spinner move even a fraction of an inch under any load.

The floor pieces between F1 and F2, and between the gear block and F3 is a 1/8" carbon/nomex panel, with lightening holes. Honestly I think it's overkill at this point. Lite ply and 1/8" balsa behind the gear block is plenty.

FWIW, I do laminate the electric firewalls here now and they come laminated in carbon. I don't cut out the discs though because that depends on your mount. I can say that the mounts we used on this plane are the cat's nippies for outrunners. Solid as a rock, but they weigh a couple ounces. You can pick the plane up and swing the whole thing by the spinner (not that I'd recommend that, but you could....)

-Mike