First thing I did was find a door that matched the other side access. I wanted it to span as much of the underside bed area as I could.
I found a 42" door on Ebay from a seller that deals in RV surplus. The price was something like $35 with $30 shipping. And it is the same manufacturer as the other door on the camper, only bigger.
Once I had the door I needed to figure out where to cut. With a door this wide I was concerned with weakening the structure of the campers sidewall. But since I was going to extend the bed platform to this wall, I'd have the opportunity to install a header from the inside to create support.
So I grabbed my "Ponder Chair"....The chair I sit in when I'm pondering what to do next. And stared at the side of the trailer for a good half hour. "Do I really want to cut a huge hole in the side of my new trailer!!??"
I said "YES" and marked out the opening to be as flush with the floor as I could get it. I used one of those new vibrating paddle saws you see on TV. A few weeks ago I was at Harbor Freight and they were giving them away FREE! It did a fantastic job cutting the aluminum and the wood. Easy and no marks on the aluminum like the shoe of a saber saw might have left.
Slapped the door in, sealed it up with Marine 5200 from 3M and I was good to go. Easily one of the very best modifications I made to this trailer. Allows access to a HUGE storage area that was previously only accessible by lifting up the mattress (Which actually opened in the wrong direction), holding it up with your head and trying to lift things over the sides of the bed frame. What in God's name was Forest River thinking!
All the before and after pictures and story are here:
Forest River Cherokee Grey Wolf 19RR Toy Hauler | RVB Precision