I don't usually post things like this, but this one worked out to be a worthwhile improvement so I thought I would share it here.
After using one of those roll out mats for several years with just OK results, it finally occurred to me that if I cut it down to the size of the sink boards it would stay in place better and be more useful. I had to cut about 2 1/2 inches off of mine and have a good snug fit. The rubber ends just slide off and then back on.
It really makes a difference once you set up camp and you can use the sprayer to rinse things from the top.
Hopefully someone else will find this useful.