Shimming camper to minimize side to side movement

I use a couple 2 x boards sawn at 45deg to take away the side to side gap between the wheel houses in the box. I want to top the angle with some "puck board" to make it harder and slipperyer than raw wood - the aluminium angle on the bottom of the camper can bite the wood if you don't be careful as you lower away.

I don't horse my Fastguns down too tight - I set them to spec with the water tank full and let the internal springs do their job.