Once and a while, & not far, It sits on my hydrohoist 90% of the time.
Not coming down on ya, but realize you are definitely over your tow rating. The 35 Fountain is 8600 lbs. dry W/O the 1750-2000 lbs. trailer and then add fuel. The Denali is only rated for 8000 lbs. if that. Coupled with the coil spring rear suspension and the bigger wheels and tires, you are definitely past marginal. The factory hitch is also not rated to tow that weight as a weight carrying hitch.
If you have and incident/accident that is not even your fault, and the authorities find out, your insurance is null and void, and you will be ticketed. I would not wish that on anyone, especially not a fellow OSO brother.