I didn't know this when I ordered my boat/trailer but Boatmate offers an underside spare tire mount that your dealer could probably order for you at a reasonable cost. The problem with doing it afterwards is that it's a weld-on option and I really don't want to grind/weld/repaint on my brand new trailer. My dealer wasn't even aware of this option (they only offered the clamp-on option near the tongue) but I spoke with Boatmate and found this out myself.