i run a force 21r in my truggy on an os a5 plug at 15% nitrox
and used the ron parris method .never hd a problem except plugs going bad
i put this against a 1/8 buggy powered by axial 28ss on 20% nitrox and kicked its ass.both motors are pullstart with kit pipe and no mods .my other motor is a jammin 12 pullstart for on road also made by force engines and dont have problems with that,even after 8 months storage primed up glo niter fitted started on 4th pull.yes force are cheaper but dont ignore them there strong,reliable and easy to use