that turning and sliding is called "scrubbing" or dry turns. They kill tires.
My GMC K2500 Manual says the Diesels should be loaded thus: 10% to 15% at the tongue, not to exceed XX LBS ( I already forgot the max). Anyhow, this got me to thinking, what does the ford and the Hummer say? I went out and one says 5-10% and the other says up to 15%. I guess it would be important to review your operators manual before towing, but 15% would be a smart figure to use if you don't have one.