I have run engines inverted and never had real problems at all, they main problem is when you start it for the first time. I do not use an electric starter but only a paint brush handle as a chicken stick (I finally bought an electric starter). Starting problems for me has always been the innability for the engine to prime properly. Prime it and the fuel drips out. Once started for the day then next time is easy. Inverted engine running needs just a little patience, I am not a great engine person but it can be done.

rc34074 - what sort of figures are you getting with your G90? Thanks!