The biggest problem with an inverted engine is taking off the glow starter once the engine is running . The second biggest problem is learning how to prime the engine because you're trying to get fuel to run uphill from the carb. This means that even if you let it sit so long it syphons all the fuel out of the tank then that fuel falls down onto the ground. All engines (upright or inverted) should be primed first before using the starter. The brute force method (grind it over until it fires) can work but I've seen an engine destroyed by using that method. Blocking the muffler outlet to force fuel from the tank is an acceptable compromise but then you have two hands close to the prop so be careful. If you overprime and flood the engine then you run the risk of damaging the conrod from a hydraulic lock.

I keep emphasising the prime because that's the only trick to it. Once you know what the engine needs then it's usually a one flick start every time. Or one bump from the starter.