I have built and flown most of the TF warbirds over the years. Here's a few ideas that might help you. Although these were originally designed for 61 size engines, most guys used 75 to 91. As you found out, three bladed props are not very efficient on two stroke engines, use a two blade 13x6 on a 75 and a 14x6 on a 90/91. Although they build heavy, work to keep them light. All standard servos work best, with two on aileron. Forget the whole flap thing. Keep it all simple, mount engine on side instead of inverted if possible. Fly nose heavy at first and adjust that by moving battery back later if needed. Keep speed up on take off and landing, learn to use rudder.
Last edited by ronwc; 07-06-2016 at 09:19 PM.