Hi. FWIW, I think you would do well with the K & B 61, either the Twist or the updated version. These are some of the most powerful 61s on the market, VERY light and VERY fuel efficient. If you prefer 4s, then go with the Magnum 80s. These are VERY powerful engines that are "tweeners" (smaller than 91s, almost as powerful and LIGHTER). The OS 72 is good as well, just a little "light in the butt " on power for a plane this size, although they will give it enough power to fly. The OS 61Fx is ok too, but the K & B tops it in sheer power output, and is just as user friendly. Also, you can't beat the price from MECOA.