Personally I have a Saito 91 on mine and like it a lot. The 91 is very close in weight to a 46-50 and is a four stroke so has better low end throttle response and plenty of power even at 5000+ feet. I did have an OS 50 in it for a while and it was fun and would hover OK at almost full throttle, but not like it will with the 91. Main problem with the 91 is cost. The Magnum, ASP and Leo are much cheaper and would do respectably well.