RE: Biplane trimming help
Haven't done the BME version. The Challenger Pitts (Indy products, pre-Horizon) is pretty much the same plane as the original Oracle Pitts. Pitts fuselage with Ultimate wings. Flys like a Stinker but lighter. Wild and crazy aerobatics but not designed for 3d. A little better roll precision than a straight Pitts. The bigger they get the better they are.
In about 38 years of rc you get the chance to do a bunch of bipes if they're you're thing. I've always had a fondness for bipes. They do some things in a manner no other plane can. Tumbles being one of them if they are heavy enough.