RE: Sundowner 50: MAgnum .70
Usualy 4 strokes are made for torke, not for speed, saito usualy gets around 10k rpm thats is almost the limit of the engine rpm, even you put a 8x8 you cant get more than 12k rpm.
If you want speed put a OS 91 FX with a 10x10 and then you will have speed, rpm´s, noise, big fun.....
Just my opinion.