Well, one of our club members had a Tower Hobbies .46 engine mounted inverted & it siphoned rather badly. I dont think it matters whether you're using a 2 or 4 stroke, inverted the carb is going to be below the fuel tank. Besides, I hate trying to put the glow igniter on
underneath when starting the engine.

I noticed a couple of fellas last summer flying the 60 size UCD laid their planes upside down on a cradle to fuel & start them. And both of them left the cowl off because of overheating.
One had a OS .90 2 stroke, the other a YS .90 4 stroke. I will try it with the cowl on but will put ducting inside the cowl to force the air up around the cylinder head.