RE: magnum prop question
If it climbs at full throttle, it is out of trim. I seem to remember mine also needed a little down trim. I never bothered to check the incidences... maybe the H-stab slot is a little off mark...? It doesn't take much at 160 mph...
What kind of prop are you using now? You will probably see the most speed from either an 8x10 or a cut down high pitch Q500 prop. An APC 9x6 is a good starting point, but not the optimum for all out speed.