Just to clear this up, the Cheetah's are the sleeve type, T-Rex's can be bored just like stock banshee cyls.
My engine guy tells me that for just bolt on and go power the cheetahs are ok. He builds a lot of T-Rex motors and likes them for everything from trail motors to big stroke applications. Cheetahs aparently have some un-necessary water jacketing around the exhaust ports, an extra transfer port ( makes less intake velocity), weak head design compared to the T-Rex, and a much smaller powervale than the T-Rex. He thinks the T-Rex is more receptive to porting ( from trail to dune to drag) and in big horse power applications ( over 110 HP) thay are a stronger application, the water jackets around the exhaust cost material thus weakening the cylinder ( K&T thinks tha same thing, call them and ask them if they are still running Cheetahs, then ask them why not). I personally do not have any first hand experience with either brand, was just trying to relay some information to you guys. I do know that I saw a T-Rex cylindered 10mm stroker on booze run olds (Glamis) at 82mph over Easter weekend. If you want more information call Kevin @ Custom Creations ATV (909) 797-1585, or you can E-mail him through his weak web site http://www.customcreationsatv.com