I've installed an OS 46FX inverted in my H9 Aresti and have only had one problem with it. The scoop:

The tank just happened to be a tad too high. This makes the fuel very slowly run out the carb and drip on the ground. I consider this a good thing. Why? I don't have to prime. And the fuel will not flood the engine - it goes out the carb.

I ran a few tanks through it on the stand and broke it in according to the instructions. Then I adjusted the idle mixture. Now that it's in the plane and flown a dozen times or so, this engine has had about a 1/2 gallon through it. After a few flips with the glow disconnected, it almost ALWAYS starts on the first back-flip. If a back-flip doesn't start it, a forward flip does.

The one problem I had: I stored the plane sitting on it's wheels after flying. This allowed the oil to collect on the glow plug. Then it would not start. The solution? Very easy: Overfuel a bit so that some fuel runs into the muffler. Lean the plane a bit so the muffler is raised up. This will allow the extra fuel to find it's way into the cylinder and flush out the oil. Then follow the next procedure:

After fueling, to prevent hydro-lock, I always stand the plane on the left wing so the muffler is down then flip the prop a bit. This allows any extra fuel to run out into the muffler. Then I rotate the plane to it's tail. The fuel and oily gunk runs out the muffler. After this, the first easy back-flip usually starts the engine. I'm guessing that this primes the engine.

Yea, it may sound complicated. But it practice, it's no more difficult than priming an upright engine. Having the fuel tank a tad high makes starting so much easier than my other upright-engined planes (which would flood with a similar setup).

This is my easiest engine to start.