IMO different engines like the tank located at differnt levels. On an engine I'm having difficulties with now I have the top of the fuel tank level with the center line on the carb. It runs fine when on the ground. But if I lift the tail so that it's level, the transistion goes rich and the engine stumbles.

Can't speak directly to the elevation but one would think the carb would tune for it. I wouldn't worry about that.

Different engines run at different temps. I have a temp gun that I use but can't get very much information from that. Once I had an engine that no matter what I did it ran very hot. It would melt the silicone coupler off the tuned exhaust system. The pipe would turn white hot! My wife picked it up and it took the skin off her arm from elbow to wrist. On a really hot engine, they will flame out or seize. Other signs is burned oil (black) coming out of the exhaust and excessive staining from burn oil on the outside of the engine.

You might decide to run your engine on a bench to eliminate variables associated with the plane. Then you'll have a better idea what your up against.