Yes, the .50 SX is my Fav engine for .40 sized planes, it is the same size as most .46's, and puts out much more power. Even at my altitude of 4,000 feet above sea-level, it pulls my .40 sizers vertical. I doubt I will buy another .40-.46 engine due to the experience I have had with them, oh and being an O.S. Guy. The only drawback is the price, as most have said. You can't go wrong with the TT, AX, or ST .51 for the price, they all are good engines. If you get the SX or any other ringed engine, just be sure to run it rich for the break-in, per manual. When flying keep it a few clicks on the rich side, never on the lean side, for the rings sake. LOL Good Luck, and Happy Flying!!!