Firstly, if you go 6'6" don't go running into the trailer to grab something. I'm 5'11" and I banged my noggin' a good one on the ceiling!

My trailer is 24'. Toolbox is on the left wall under the cabinet. Wing goes on the right against the side wall. Wheeler goes in between and tows the car in. Tire rack is above the right wheel well, fuel jug racks below it. Compressor & generator go in behind car, nice to have good light for loading. Might consider a wing holder on the ceiling overhead, it does protect the wing if you have clearance.