camperD
The door opening is 25 1/2 wide by about 11 inches high, but the skirting on the Classic is a different height and you can make the door any size you want. Here are a couple more pics of the door. the first one shows the piano hinge at the top, the black push on molding and one of the latches.
The second pic shows the weather strip on the edge, there are screws under it that fastens the skirt to the square tubing inside the edge.
The third pic is of the 1" square tubing bracket inside the skirt edge, it is screwed to the plywood floor. Any other questions just ask, I will help anyway that I can. You can make the square tube brackets without welding, use steel tubing and cut down all 4 corners on one end about 1 1/2 inches bend 2 of the sides opposite each other 90 degrees and cut the other 2 off, drill holes and you now have a bracket.