Do your own arithmetic and don't trust the sales guy.
First of all, there no single answer for "a half ton truck". Regardless of the truck manufacturer, each configuration of their half-ton class of truck will have a different tow rating and different payload. Even installed options like the trim level have an effect, so you have to talk about a specific half ton truck year, model & configuration. Second, the load you place in the truck, passengers and gear & trailer hitch, also play a role by reducing the payload (cargo capacity). Once you have that figured, use the trailer GVWR as the probable towed weight and 20% of the GVWR as the probably pin weight the truck must carry. If those fit within the particular truck's capability, you should be OK. If not, it doesn't make any difference whether the RV manufacturer or the sales guy says it is "half ton towable". Cause it ain't.
Only a few half ton truck configurations have the capacity to tow even the smallest 5W, mostly because they lack cargo capacity (payload) for the pon weight + passengers & gear. And most fifth wheel trailers labeled as half ton towable aren't towable by most half ton trucks, though I'm sure they can find one truck somewhere that passes muster.
