Don't worry missleman, i have reglued the firewall and added some extra reinforcement, i can't see it coming loose anymore than on a bigger plane with a 1/4" ply firewall. This engine is a GAS/GLOW conversion engine from an old weedeater, it probably needs a new ring to make full power and with the ThrustHP calculator i can tell you that my TT PRO.46 spins a 12.25x3.75 @ 12500rpm which takes 1.18hp, my 21cc turns a 16x8@7000 which is 1.285hp, so the #'s are pretty close, for ground clearance i'm going to a 13x8 3 blade prop, i will make sure i get some video of the maiden, just waiting for a few more parts from tower, should be ready in two weeks.