Hi, Mandy:

I may be all wet; but, here's an idea:
I would build a wood frame that sits down inside the angle frame and comes up just level with the top edge. Put 3 coats of CPES on it so it doesn't rot. (I think you've already done both of these.) Next, I'd Bolt nice, strong and straight CPES'd 2x4's (or 2x6's?*) all the way around the outside edge, bolting them all the way through the metal and the inside wooden frame. *These should cover the outside frame and come up above it some as they will probably become a trim feature

on your trailer. This
may straighten the metal frame(?). If it doesn't, you can always trim down the outside bolted wood boards in the places where the metal bulges and fill in any areas in the inside frame area that aren't filled with wood. (If the spaces are big spaces, glue wood in them.) Do
not trim down except where metal is as the area above the metal frame is where you will be squared off properly. Now, you can sit your walls against the trim boards and attach them to both the floor and the side trim boards and hopefully be square.
Again, this could be all wet and wrong.
If this idea belongs in the scrap pile, please, people, speak up and say so, as I wouldn't want to make things worse
for Mandy.
Thanks
