Most problems occur because there is a siphoning effect into the carb when the tank is full. At higher rpm it is not a problem, however This makes consistent smooth idle tough, especially low idle ! If you place the tank lower than normal in the fuse, this will help eliminate this problem but it will create others!

some engines seem to do very well mounted inverted while others can be a real pain!! Best thing to do is set it up on a bench first and see what you got ! you can always add on-board glow but this will add $, weight and complexity to the project !