I recently posted about the 350M and hitch. I have a 2016 Ram 3500 Mega Cab and a 2016 GD 350M. I tested it carefully and determined I didn't need a slider this time. I've had a Pullrite Superglide in the past with a previous short bed Megacab and a different fifth wheel.
It's important to note I'm using a Reese Titan hitch mounted on rails with the Ram fifth wheel prep package. This combination as well as the rounded front cap design by GD allows for this to work. I backed the truck up intentionally as tight as I could to either side and completed a U-turn and the coach never came closer than 12" from the cab of the truck.
We've had the GD for 6 months now and love it. The energy management system works as designed. We use the coach frequently for local trips and have taken it to NC and GA mountains.
The only change I made was taking my nearly new GY G614's, load range E tires from old coach and placing them on the GD.
We have a golf cart in the garage area. The coach pulls like a dream and at roughly 38' it's easy to park and back up at most locations.
DW and two boys
2019 Grand Design Momentum 397M
2020 Ram 3500 DRW