I'm pulling my 27BHS with a 1/2 ton. It is maxed out and I feel it behind me, but for the most part, I haven't had any issues towing it. My tongue is at about 12%.
My parents towing will be mostly short trips around Michigan with no mountain towing. If the 28RLS is at 12% tongue weight, it will be right there for vehicle GVWR. They are comfortable with that, and they will have to do some careful packing. They don't plan on getting rid of the truck and they love the layout of the 28RLS, so they will find a way to make it work.
2015 Chevy Silverado LT Z71 CC 5'8" 5.3L 3.42 Rainforest Green Metallic
2016 Jayco Jay Flight 27BHS Elite