Joe, sorry to hear that the budget is an issue for upgrading your axle/brake configuration. If, as you say, your rig is grossing out at 20,000 pounds it is crying out for substantial axles and disc brakes. Safety vs. budget is always a tough call.
The first trip we made in our '07 MS was from the dealer to Mor/Ryde in Elkhart to have the axles changed to the Mor/Ryde IS system.
I ordered the trailer with disc brakes/17.5 in wheels and H-rated tires but the axles were the standard 8K Trailair leaf spring axles. For the same cost as the Centerpoint axle option from DRV I had substantially sturdier axles installed even though the weight rating was the same at 8K. Everything aspect of dealing with the changeover at Mor/Ryde was professional and courteous.
Billr is right -- MR is changing out axles every day. It won't cost you anything to discuss your issue with them and you may find they have a solution for you. I am really pleased with what we achieved.
If you want to see a picture series of the changeout process check out my
Webshots site.
If that doesn't excite you there are some nice photos of Bill and Joan's beautiful KOA Kampground at Sault Ste Marie, ON :)
Good luck with your upgrade project.