AN OS 48 or 70 would work. The Best is an Saito 56 although a saito 50 or 62 would work, I have had this model since original build in 1987. I started with a Saito 50 and wore it out and put on a os 70 and it felt nose heavy and just plain heavy. Now it has a Saito 56 black knight on it and it is fine. APC prop and 30 heli fuel and you can almost hover for 30 seconds.