I once bolted a 20-10 (too small for flying, but just right for a light load and break in) on the front of a Zenoah G-62.

Hooked up the fuel line. 32:1.

Started it up and let it warm up about 2 minutes.

Full throttle.

Tuned it about 500RPM off peak.

Walked off to the shop to finish my new kit.

When the noise stopped (5g of gasoline later), I went outside and unbolted it from the stand.

Took it inside and bolted it to my plane.

Still flying it. About 40 gallons later. Runs great.

I don't break in my gas engines on a stand anymore. I think they run so good, you don't need to worry about the flame-outs and poor carbs like on a glow engine. Gas engines just RUN. Tune it up a bit and go fly it.

My point is, either way works, if you just apply a little common sense to the equation.