We used to have a 2012 Mega Cab 2500 that we used to pull our old 2014 Cross Roads Cruiser bunk house. It was a 40' 5er and was just at the 11,500 mark. We never had an issue towing it and we stayed mostly in New York, Vermont, New Hampshire areas. She pulled up hills no problem and handled excellent.
Mega Cabs have the same Bed as a Crew Cab short bed The Mega Cabs just don't have the 8' bed option. We have had two Mega Cabs. We recently switched to a Crew Cab and hate it. But we have used all our old Mega Cab parts on the new truck.
As for a slider hitch it's great to have, we installed a slider in ours but have never used it. Our last 5er was set back over the pin which allowed us the clearenace to turn and not have to slide it.
Our new 5er is set forward of the pin and does not allow us to turn as much before contacting the rear window.
Our new 2016 3500 TCD is an amazing truck but we wish we stuck with the Mega Cab.
I can't get our photos to post to the thread to show you