Camper fit concerns on a 2017 Ford f 250

You can always put a 3/4" plywood and a rubber mat in the bed under the camper. But I would measure first anyway.

Two inch clearance should be sufficient. Consider a tie down system that is bolted to the frame. They cost a little more but will give you peace of mind.

I have Lance 1161 and had to shim it about 3" to clear the rails on my 2017 Ford.
I just went to measure my Lance.
Camper sides are at 20" height and truck rails show 21", but you can expect camper sides to sag a bit, so calculate 2" extra clearance.

I have a 2016 F250 carrying a Northstar Freedom. I have a 3/4" mat and a 2" frame under the camper which gives me about 3" -4" clearance over my cab. Highway seams,dirt roads,etc can cause some forward /backward rocking. I would be very concerned about the survival of my cab marker lights with any less clearance.

When I picked up my Lance 820 for my 2016 shortbed F250, the previous owner gave me a sheet of 3/4" plywood. It was not enough to prevent rubbing on the cab for a bit.

The rubbing was not significant, but still annoying.

I built a platform out of 2x4 with 5/8" plywood on top, 2 by 4s laid on the 4 inch side. That gives enough clearance.

You will have to do the same thing, more than likely. It's not very hard. The 2017 trucks are even taller than the 2016s.