I have had a SupreTigre Gs40 and an Evo .46 trainer engine on my Lt 40. On both engines I switched from a 10x6 to a 11x5. I found this helps a lot on landings, slows the plane down, and it doesn't float so bad.
The only problem I had running the bigger prop, was prop strikes, the wire gear just gives to much on landings, not to bad on pavement but not so good on grass. To solve the problem I converted mine to a tail dragger.
I agree,Sig kits are my favorite too.