New Axles - What gross GAWR to choose?

I have a 1986 29' Sovereign with a GVWR of 6800lbs and GAWR of 3200 Lb. It is time for new axles and I'm trying to determine the axle rating. We finished a rennovation last August, so exept for solar panels I have already added most of the heavy things (bigger batteries, counters, more cabinets). Upon the return of my last trip I measured the trailer weight (@highway scale of 6840Lbs) without truck but with the weight distribution hitch fully set up. The trailer was dry but still had 80% of the packed load. I figure if I fill my water tank and pack up the fridge & food areas in a pre-trip situation it could be closer to 7500 lbs sitting on the trailer axles. This makes me want to specify 4000Lb axles as 3500Lb units would not be enough.
Would you agree that the 4000Lb axles sound about right without being too much?
Can you specify ratings at steps between 3500 & 4000?
Thanks for your help, Scott[/QUOTE]