On our Onan, we use the rear (27 gal) tank. It has 2 pickups; one short that usually is used for the genset so it can’t leave you with no fuel to get to the gas station, and one long, usually the feed for the engine.
We switched them because that is our third tank. The first two are both 35 gal. We feed the engine from the rear tank first until the level’s below the short straw, then from the middle tank, then from the front tank. That way, we lose the weight from the rear first.
RV and marine supply places should have a two-pickup system to install in your tank.
