On my 2005 Islander, the main tank(150G) is located farther aft and the aux(50G) is forward of the main tank. I always keep the aux. tank full and run off the main tank. I get a much better ride that way with the weight of the full aux. tank keeping the bow down. Once in a while I'll run the aux tank down after the main tank is near empty so the aux. fuel doesn't go bad. This gives me the best ride and fuel economy!
Pete
Pete