It's hard to find a sub 29' fifth wheel with decent holding tanks for dry camping. Most of the shorter units trim weight by reducing tank capacities. My AF 27-5L is 28' long and has pretty good holding tank capacity, but the GVWR is almost 13K with the dual pane windows. Honestly, I think it would be too much for your truck. My brother has the smallest Alpenlite (Valhalla) that I'm aware of. Nominally, it's a 29 footer, but the actual measurement is probably over 30. It has huge holding tanks (100 gal fresh, 100 gal gray with 50 gal black), but the GWVR is 14000 lbs.
