The sponsons on my rigger aren't quite big enough and the profile is wrong. It wants to submarine instead of plane out. More show than go as built.

4-strokes work great! My first boat; a Kamikaze. Designed by the same guy that designed my rigger. The rigger was built from scratch without plans. The original rigger went over 80mph with a Jett .90lx. Mine had a TT .46 though my Jett .35 is as strong or stronger than the TT .46 so I may use it instead. The little 3-pointers turn pretty well if a turn fin is used. Else it suffers a good bit in turns.

Kamikaze flat bottom run with the two 4-strokes I own. First video is on water using an Enya 60-4C.
http://youtu.be/fVadTr40eQw
Same boat but with an Enya R120-4C. Twice the displacement, 13x7-13x9 APC props and a whole lot faster. On grass:
http://youtu.be/Ub0mfQ7Lp1g

Boats with 4-strokes need to be really overdisplaced over a 2-stroke to get as good or better performance. Example: if it runs great with a .60 2-stroke, it'll ROCK with a .90 2-stroke. In place of a .90 2-stroke I'd use a 1.20 4-stroke.