Raising truck camper height

I screwed 5/4 decking in three places side to side, end center and end, not lengthwise, directly to bottom of camper. THEN, installed a 3/8" formed rubber mat from an auto parts place (I think Advance Auto, but not positive) and have ZERO problems in ten years.

That's on a short bed Lance - if it were an eight foot bed, I'd install four...

I have a standard rubber bed mat in my truck and then put a 4x6 horse stall mat on top of that. It gives me plenty of clearance with our Northern Lite 8.11 on our 2017 F350.

I would consider TC weight distribution for choosing the foam.
When 8' camper will give relatively even weight spread over 8' bed, the 12' camper, with COG behind the rear axle tend to rock on last few inches of the bed. I had couple of my 2017 F350 bed ribs bent having 12' camper on factory mat, so imagine what that would do to a foam?
What I noticed is that bed ribs end like 2" before bed end and don't have solid support under.
So I add a stripe of 2" plywood at very end of the bed, where bed has frame under, so now my camper has good support at rocking point.

There are different qualities of foam. As far as I've seen the best has a 30 psi compressive strength. So whether or not the foam deforms will depend on your camper's weightbearing footprint. My Northern Lite seems to bear just on the fiberglass edges, so I won't use foam. Plywood and a rubber mat work fine on my '17 Ford.

TCINTN wrote:

3 tons wrote:
Thats what I do with a camper weight (wet and loaded) about 5,000 lbs. Foam does not compress...BTW, I put a rubber mat on top of 1” foam board...

3 tons

Ditto. I have had 3 sheets for 5 years

I will add that my 5,000 lb camper has rested on this foam board (builders foam board 4x8x1 from HD) for at lest 5 years...No problemo.

See the other multiple threads about the same thing.

Mine unfortunately did not survive without crushing, MT Camper. I ended up using the 1 inch foam board, but picture-framed it with 5/4 x 6 decking allowing the camper outline to rest on 1 inch wood. YMMV

3 tons wrote:
Thats what I do with a camper weight (wet and loaded) about 5,000 lbs. Foam does not compress...BTW, I put a rubber mat on top of 1” foam board...

3 tons

Ditto. I have had 3 sheets for 5 years

Thats what I do with a camper weight (wet and loaded) about 5,000 lbs. Foam does not compress...BTW, I put a rubber mat on top of 1” foam board...

3 tons