Got the same set up U-CAN-DO 60 with a Saito 100. Just fried a set of bearings in 1 season trying to lean the engine to compensate for the siphoning caused by the tank. The tank is in the wrong place, this caues the mixture to be richer or leaner depending on the fuel level in the tank. When the fuel level in the tank drops below about a 1/4 tank the syphon effect is almost gone and the engine is then too lean. Unless someone has riged up an on flight mixture adustment it will contionue to be a problem, until the plane goes under the knife.