RE: 20CC: fuel flow, thrust?
I have a well broken in G20ei on my RV4 with a 16oz tank and after a 15min flight I still have over a half tank of fuel left . Most of the flight time is WOT.
The thrust you get will depend on the brand and type of the prop as much as the size of the prop. So asking for thrust based only on the size is pretty much meaningless.