2005 Sportsmen Sportster 24' 3500lb axles?

I have a 2005 Sportsmen Sportster 24' and have had several catastrophic tire failures. After some research, it appears that this toy hauler came with the wrong axles. The VIN sticker says that the GVRW is 10,000lbs, but the axles are 3500lbs each or 7000lbs. I bought the unit in 2008 and it came with 205/75R-15 Load Range Cs. After losing one of those on the way home, I upgraded to 225/75R-15 Load Range Ds. This effort was in vain. After having three separate blowout/tread separations and rebuilding the wheel wells and fenders, I upgraded again to Load Range Es. This has worked for the most part, but the larger tires have rubbed the inner fender wells.
My question is, did any of the 24' Sportsmen Sportsters come with 5000lb axles? If so, why did mine come with the smaller ones?
I carry a golf cart, Jr Dragster race car, tools, generators, etc. and my total weight is around 8500lbs. It is a handful to tow.

Thanks for you help,
Joe