I think your GVWR is wrong. I understand it needs to be what your truck is tagged at. And your truck needs to be tagged at what the total combined actual weight will be. Example truck weights 5k, loaded tandem trailer weights 7k, puts you right at 12k. Im guessing your truck is tagged at 12,000, which is fine with your single axle. My work truck is also tagged at 12,000, but with a full load of grass and my tandem trailer loaded up, I'm really pushing it, and might ought upgrade my tag to 16,000 to have some wiggle room. I understand they can actually give out overweight tickets if your over what you are tagged at.
Kansas Certified 3b Applicator
223 52" Grasshopper
48" MTGHS Walker EFI High Dump
32" Toro T-Bar
PJ 16' Trailer PJ 12' Trailer
2010 Kawasaki Brute Force 650 with Warn snow plow
2000 Ford F250 with aluminum dump bed