RE: Four stroke OR Two stroke for speed!
Best 2C setup I know of to date.... several of these flying...
Jett SJ-90LX - T configuration, same setup used on the GP Toni
prop 11x8, 11x9, 12x6 between 14,200 - 14,700 rpm
Reports on speed for this vary a bit, but are between 130 and 140 mph (radar gun in each case)
The YS110 might be a good 4-stroke choice. Load that thing up with a 13x10 and let it turn.