RE: 2 Stroke inverted mounting
Aside from all of the little annoyances, there is one big problem to be aware of - Hydrolic Lock
If you get too much fuel in the head, the piston can't get to the top of the cylindar (Or more accurately, the bottom of the bucket of fuel)
Since there is no outlet at the top of the head, the fuel has no way out unless you flip the whole plane over.