While 1/2 ton trucks are probably the more commonly seen tow vehicles on the road, I'm thinking that most are greatly exceeding their payload capacity! Especially those that are pulling 5th wheel rigs!! in the case of the 21' Viewfinder, its GVWR (Gross Vehicle Weight Rating) of around 6000 lbs results in a hitch weight of 600 - 900 lbs (10-15%) if fully loaded. That weight MUST be considered part of the TV's payload. Add to that, the weight of the driver, all passengers (including pets), ANYTHING that's placed in or on the bed of the truck (topper, bed mat, tools, generator, extra fuel) and the trailer hitch. Fuel in the fuel tank also counts against payload. I'm not sure of the exact GVWR for 1/2 ton trucks but it's around 6000 lbs. (You'll find it indicated on the plate on the door frame). So, when considering a TV for ANY trailer, first check the GVWR, then take the truck to the local scale or CAT scale (found at many truck stops) to get the actual weight of the truck with you in it and perhaps a full tank of fuel. The GVWR minus the truck's actual weight will tell you what the available payload is. Add up the things mentioned above that weren't in the truck when weighed (be generous) and again subtract that from the available payload. If the final number is greater than zero, you're "legal" but 10-15% extra available payload is recommended.
Not mentioned yet is the GCVWR which is the combined maximum weight of the truck and the trailer. That weight rating varies based on the configuration of the truck but like the GVWR, is a legal definition.
Basically, with the mentioning of perhaps moving up to a 30' trailer, I'd say you should be looking at a 3/4 ton truck. Gas or Diesel would be the topic of another thread!
RipVan