Edible - I know that a big dia/big pitch would load up the engine too much, hence my comment that Jimmy really needs a bigger engine

A 90 four stroke will never give a 8.5lb model real vertical performance. I have an 8.5 lb chipmunk myself, so I know how they go. I have a 91 FX in mine, with an APC 15x7. At that weight the wing loading is about 28 oz/sqft.

Per CG, its weight should be between 6-8lb. If it did come out at 7lb, then the 90 4stroke would probably be fine. Wing loading would be lower, so it wouldn't need so much speed either.