My first suggestion would be to NOT put the heating/cooling (or any for that matter) vents in the floor. For those that have kids, dogs or actually use their trailer all the dirt goes in the floor vent.

My second suggestion would be to either put locking hinges on the overhead cabinet doors that open upward or to use side open cabinet doors. It's hard to put stuff in the cabinets when you have to hold the door up with one hand.