Well, I'll take back what I said bout something. You can overpower a plane if you go way oversize but my case I have not. (Maybe you should have gone up to a 51), and cos my plane is bigger, I went up 2 sizes, plus the airframe is strong too (I did some changes), it can take a 61. I found some websites showing fliers flying a LT-40 with an 61, and having no problems at all, even using the same engine mount and undercarridge (Which myself did change).