Frank Lee -- throw away the axle, put a [retractable] single caster wheel pointed up on the bow and add two bumper clamps to the transom. Turn it upside down to make a single wheel correctly boat-tailed trailer.
mikeyjd -- I've got a lot on my plate right now. Like, breakfast.
For now, just forget everything I said and consider my reply to Mr. Lee. It solves the air-gap problem pretty neatly, but any cargo would have to be lashed down below the benches before you turn the boat over.