I did the small camper in a half ton thing for 4 years. Put airbags in the truck, which helped a lot. With the camper about half stocked it was close to GVW before hooking up to the boat.
In my case having the 4 speed transmission sucked. On perfectly calm days I could get by using 4th gear. A little wind and it'd be up and down between 3rd and 4th. A lot of wind and it would be constantly between gears on flat ground.
I think the biggest problem with a small camper is it always leaves you wanting more. Mine was hardly enough room for me and my dog. The few times my dad came along on a fishing trip it was really crowded. No toilet. After the second year I bought a small dometic portapotty that fit under the step to the bunk. In the end I'd had enough and decided I needed a bigger truck and then could watch for a bigger camper. I ended up buying a 3500HD long box and kept the little camper while watching for an upgrade. The first difference I noticed was that the factory suspension didn't even notice the small camper at all. In perfect weather I think I lost about 2l/100km from the half ton to the one ton. But in the wind it was a huge improvement. The 6 speed transmission was never gear searching.
I found my upgrade last year. Bigfoot 25c9.6. The factory suspension handled that well too, but I did decide to install timbrens, wedges in the lower overloads and extended bump stops to engage the top overloads sooner. That took care of the slight sag and smoothed things out a bit. In the end it is a bit nicer to drive. I expected a bigger camper in a bigger truck to be affected by side wind more, but it is a bit more stable. I like the ride a bit more, I'm not a huge fan of airbags. All loaded up, hooked up to the boat, this setup is around 1500lbs shy of the GVW.
Lots of people said I shouldn't bother going with a small camper in a half ton truck. It worked, it wasn't comfortable and it wasn't enough room. The airbags deflated to minimum pressure made the truck ride like a one ton anyway when it was empty. In hindsight, I should have just started with a one ton.
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bman32_320, on Flickr