Did you ask your local (or closest) Sooner/Exiss dealer if they had anything available?  I'm not familiar with the 99' Sooner dividers but you should be able to add eyelets to the bottom of your divider and then use a pin (similar to how you hang a door) to hang your studwall.  That way it's removable if need be and makes it easier to remove your dividers.  Knowing the length of your divider you can order a studwall from just about any mfg or have one custom fabricated as was mentioned. 

"Go to a local welding shop and see if they can make you ramp I had one put a hay rack on for me..even see if they can help with your other problem. "

did you have the welder make the hay rack, too, or did you just buy one and have him attach it?  I have been considering this option too on my 2H straitload.. I don't want to spend any more real money on it because I really want to get another one...Which would also be an option tp put on the new one.  I can think of soooo many little things that I would like to add to what ever trailer I have to make my life easier.. ie: corral panel holders, no-spill bucket holders on the outside, attachments to the outside of the trailer to hook your corral panels to, awning, hayrack, lantern hook attached to the outside, etc, etc, etc, etc.... you get the picture!!  If left to my own devices (and an unlimited amount of funds) I'm sure that my trailer would look like the little old woman who lived in a shoe.... or maybe the beverly hillbillies..LOL!

Hung the mat with u-bolts through the existing divider, above the lower part of the divider frame, because I have a telescoping divider. 

For a removable lower piece, you could run carabiners through the mat then attach to the U-bolts on the existing divider.