I picked up some rubber "grip liner" 1m by 2m roll from the cheapy shop down the road. Below shows a small strip of the rubber, glued to the blue foam as a test, beside which is the drawing pins that I was using.
I started by placing the board on it face, using foam cut offs to keep the terrain protected. I should have done this before I painted the board just to be sure I had it all secured.
Next I poured from the bottle of PVA a liberal amount of glue to cover the edge (cloth) and the centre of the board. focusing on points evenly spaced apart (4 rows of 4 points), with pools of glue which I spread out with my finger to thin out. Once I placed the rubber down I pushed drawing pins into these positions to help fix the rubber to the foam and provide added strength when all is dried.
Once the glue is dry I will trim the rubber so it sits under the edge and allows for the boards to met even flush.
My big concern is that the rubber mat will add uneven height across the three boards so that they do not sit at even levels when side by side. I will let you know what I find.
Step Cost = $24.50 ($12 PVA Glue, $12.95 Rubber Mat)
Total Cost = $453.35
Time Taken ~2 Hours (17 Hours Total)