Ok, I've sorted out most of the issues by relocating the engine back 1/2". Now the plane will fly inverted with slight down elevator and it no longer drops off so steeply during banked aileron turns. Still requires some elevator for banked turns, but that was expected. Before it took almost a quarter stick of up elevator to turn and maintain altitude.
Additional information for others with OS FS91ii. Switching from Wildcat 15% heli fuel to Magnum 30% Heli fuel eliminated 300 rpm drop at idle when igniter was removed. Now I am leaning out idle mix to get lower steady idle and adjusting for higher top end rpm.