You are better off with something like a SA82 if you can if not a simple 52 2C would be good. Keep the weight low and the plane does not have that much wing area. I have flown 40 sized planes with 60 sized 2C engines, there is definately more power but you will feel the weight penalty, I used a 46 2C on both planes at the end. I did it on a WM Rambler and BH SU31, both have much more wing area than your YAK so I think the weight penalty on the YAK will be pretty noticeable.