My test stand is a sawhorse made of 2x4s. Cheap, effective, and I've had everything from a .32 Wankel glow engine to 100cc gas twins on it. Accomodating odd setups like big long tuned pipes is no problem. All it takes is some 2x4 and 2x6 scrap pieces and a screwgun.

To me, safety means the test stand must:

1. Be extremely sturdy
2. Be able to mount engine securely, preferably using the exact same mounting method as on aircraft
2. Place the engine at proper working height (slightly above waist level)
3. Be able to mount the engine in various orientations (to make access to adjustment points easy.
4. Be able to be reposition and relocated as required (for example, so the exhaust blows downwind)