RE: rich or lean gas?
I can't help you with the engine but I can tell you I had a Midwest 300 with a Brison 2.4 @ 16.5 lbs. and there is no way in the world that I could get it to hold a KE. I tried everything, props, balance, servos, everything, I finally got so upset one day I stripped her down and throw it in the garbage. Others have no problems - don't know why - never did figure it out.
I had a Quadra 42 in a 1/3, 16 lb. Pitts Special and it would KE all day at about 1/2 rudder stick.