My estimate is the 25G is overloaded.
1600 for ATV
180 for fuel
840 for water
=2620 lbs.
No food, clothes, riding gear, camp gear, etc.
Dry tongue weight is 1150. Add batteries, propane, some gear in the bedroom and closet, etc. 200+ lbs? = 1350 for tongue weight. Whats the receiver rating on the GM? also it looks like your 1200 bars are weak. 1500 bars would be better. Have you set up the truck by measuring the front? And have you scaled the truck and TT?
I'd be looking at a 3500/350 diesel at a minimum since you're looking to possibly go 5er TH in the future.
