Hey Scott,
How does yours run with the perry pump? I just bought one and a 24oz tank and I am undecided as to wether or not I should mount the tank at the CG or just leave it in the stock location. Also are you using a Pitts style muffler or the stock one? I have no Idea what all these changes are going to do to the fuel pressure....
RP

Paul,
If there is no change with chopping the power, then I don't think the thrust line is an issue. I know the 3D hotdoggers like a degree or two of upthrust actually for hanging on the prop. Not sure what the problem is with your plane. Maybe the wing incidence shouldn't be zero. If you do the long vertical dive does it belly in or out to the canopy, or is it straight down?
RP