I just use #2 socket head sheet metal screws for all .049 - .061 stuff, but I use at least 5/32" to 3/16" plywood firewalls for the high powered engines. 1/8" plywood is marginal.
Same goes for beam mounted TDs on the black plastic mounts. Machine screws and blind nuts gave me more trouble and a fellow flyer talked me out of using them for 1/2A projects years ago.
With a Cyclon or Fora backplate mount, using machine screws and blind nuts would force you to use a firewall that is larger than the backplate, creating more frontal area.
I use a #43 pilot drill for the #2 sheet metal screws. The drill bit needs a few winds of tape so that a typical drill chuck will grip it.
Last edited by combatpigg; 06-06-2014 at 08:22 PM.