Hi jb88ci,
Just want to correct you in your statement about 2-cycle engines leaning out as you go up. The higher you go the richer your engine will run. As with snowmobiles in the mountains, we would have to put smaller jets in the carbs to make them run better as we climb. At over 8,000 feet we would have to rejet again to smaller jets. You do lose a little power because the air is thin and you are using smaller jets.
So I would set the ultralight engines up to run their best (not too lean) on the ground and when you fly up higher it will run just fine.
If you were to go really high then you would have to find a way to lean them out in-flight. But remember, when coming back down, you would have to richen the mixture to prevent seizure.
Have a nice day, daffy