22 gals weighs about 60kg (130lbs). If it causes some listing, just move some gear to the other side (Use the drivers side tank first)... Even with both valves open, it wouldn't suck evenly from both sides, it would empty one tank first (path of least resistance)...
Run off tank 1 enough to burn off 10-11 gallons, then switch to the second tank for the rest of your trip. You''ll end up with half a tank backup with minimal listing for the majority of your ride.
I am wondering now if this would be good for putting the boat up for the season. Run the motor out of gas so none is sitting in the carb on in the fuel injectors.
the recommended storage method is EITHER tanks nearly empty and fuel chemically stabilized OR tanks full and fuel chemically stabilized either way is fine but half a tank is the worst possible condition... Engine needs to be run long enough to ensure that stabilized fuel is throughout the entire fuel system