Not counting Q500 and Q40's, the funnest speed planes I have flown, were my:
15 sized Ace Ultimate bipe with O.S. .25fx, LOW 90's on RADAR
40 sized Scratch Built Eindecker with Jett .50, Radared at 148 mph
Whiplash, never caught on radar, didn't make it out of the split s
Hangar Nine Corsair with Jett .90, Never radared, estimated around 110, maybe faster.
Kyosho Spit with Jett .50, radared at 120 mph.