You should sorta figure where the prop is supposed to be using one of the recommended engines. Then see how much you will have to move the firewall back to sorta get to prop for the Ryobi in the same place. The Ultra Stick (orginal) often comes out tail heavy and the Ultra Stick Lite comes out nose heavy with any thing heaver than a Saito single. The lite needs a little creatitive crafting to mount servos in the tail.