The real downside is that you really need to convert the rod and crank to needle bearings. If not, you will still have to run the same high oil content as on glow to allow the bushing rod to "live". I don't know if there is room in the rod for your engine to install a needle bearing. The crankpin in the crankshaft also has to be changed to go with the needle bearing in the rod. (The original is not hard enough to work with a roller bearing.)

Another potential problem is overheating. If it will be and "open air" engine on your plane, it should be alright. If it is a cowled engine, it will need to be properly baffled to assure good cooling. Gas engines run hotter than glow, and that is why they have much larger cooling fins.

AV8TOR