The TT pro 46 is a good choice. The OS 46AX has a touch more power but costs about $20.00 more. Either one will make you a happy flyer. Don't bother with the 40 size engines. Almost the same price as the 46 but less usable power. The weight is also pretty much the same because they use the same case and bore the cylinder wider so you actually get a better hp/weight with the 46 engines. [8D]