The only negative on upside down engines is that they can flood easily.

I had a Moki 210 in H-9 Edge 540 and the fuel system would syphon through the carb and flood the engine when sitting for a while with

a full tank so I would pinch off the feed line with a hemostat till I was ready to fly or I wouldn't fuel until I was ready to fly.

Always use THE BEST GLOW PLUGS, they not only last longer but they make your engine much more reliable and reliability = FUN.