The two Grand Design 5ers are barely 1/2 ton towable. The average 1/2 ton, that is ones with 1200-1750lb payloads won't work. As is the case with lots of "1/2 ton towable" 5ers. Only a select few 1/2 tons will work. So saying that a 5er is 1/2 ton towable is really misleading.
Take the two Grand Design models for instance. One has a 1476lb pin and the other a 1516lb pin. That's before adding propane or batteries plus cargo. Now figure in 150-200lbs for a 5th hitch and with just the hitch alone plus dry pin, even the lowest pin weight would be 1676lbs without adding anything.
The average 1/2 ton is now at or near it's max on RAWR. And no one's even in the truck. Only way to make it work towing a 5er with a 1/2 ton is to start with a 1/2 ton that has a high payload in the 1700-2200lb range and also start with a dry pin in the 1200lb range.