there are many methods in use. there is a commercial availible u shape with stake ( midwest MFGD I think) ive used with no problem. as well as home made wood tail restraints with large spikes& door hinges requiring you to pull the model back some before the brace drops backward. a comercial unit was availible several years ago. any time your engine is running you must exercise caution regardless.
the dog collar snap works too with a length of commercial heavy fish cable swegged to it. snap goes around the nose gear or tail wheel.