The way I THOUGHT I understood this and may be wrong after suffering through this thread.
If your combined weight of truck and trailer is less than 26,000 lbs then you don't need a cdl for private use.
My 110tlb with cab is about 8000 lbs, carrying an additional implement (say the boxblade is another 1250 lbs since it is the heaviest implement) and add the trailer weight with spare and chains 2650 lbs. 8000+1250+2650=11,900 lbs. Trailer is rated for 12,000 lbs and that is very close! I seldom if ever carry the boxblade and the hoe at the same time but for sake of arguement lets assume the 12,000 lb. trailer is loaded.
Living in the mountains I wanted to have a truck that was safe to pull this trailer, so in 2005 when I purchased the tlb I also bought a new truck. The truck is an F550 4x4 service truck which is rated for 19,000 lbs and has a 33,000 lb tow package. The ACTUAL weight of the truck is 11,800 lbs aprroximately (depending on what is being hauled in the bed). If the truck is 12,000 lbs and the trailer is 12,000 lbs my total weight is 24,000 lbs and less than 26,000 lbs in all cases.
So do the reguations require me to have a cdl for a rig that is under 26,000 lbs in actual weight? I purchased the larger truck for safety reasons but may still get in trouble if I understand this. It appears that the "rated load" seems to supercede the actual load. The trucks gcwr is 33,000 lbs ( a Ford spec), the trucks gwr is 19,000 lbs and the trailer is a 12,000 wr pull type.