I've personally always been taught pickups were made for hauling and everything else was meant for people. IMO I wouldn't do a lot of hauling with mine. What you described the second time though is definately within the capability of it. Maybe past manufacturers reccommendations, but 12 miles, go easy, stop early, you will be A-ok.
95 Laredo 4.0, 2" RE BB, RC N2.0 Shocks, Custom Roof-Mount Light Bar w/ 6 lights, Bumpers deleted, Homemade sway bar discos, Michelin LTX 31x10.50s, and a Dog Box :)
Planned: Homemade Spare tire carrier, double shear front track bar, 4 adjustable rear control arms, New Rims and 33" Wrangler MT/Rs or BFG M/T KO's w/ LOTS of trimming.