RE: Kadet LT-40 Kit a good first float plane?
The LT-40 is an excellent platform for floats. Rule of thumb on float length is 75% of fuse length. 91 4 stroke may be a bit much, and the 70 might not do the trick. A Saito 82 would be awesome. Just make sure you prop for speed, not thrust. Good luck, and have fun!