been doing nitro for years & i've never needed to lock the engine like that
if you're tightening or loosening the flywheel nut just hold the flywheel with some grips/pipe wrench or if you're into buying daft tools one of the flywheel holding tools. they do ones that use the clutch pins or band type that you tighten round the flywheel like an oil filter wrench.
personally i just use some grips
