MR had a couple of options for me to replace the carpet tile, one was a really good quality very strong, but hard and thin rubber with a woven backing, the other was a very cheap and weak, but very soft rubber that was in a larger piece.
I chose the softer one because I could do it all in one piece.
So I unbolted the board and took it out of the bag and stripped off the old carpet tile, this was easy because I put it on using a Selleys probuct, so I knew it would never stick too well
Then I cut the bolt holes for the new one and glued it on.
I took the opportunity to lighten it with a few holes before I bolted it back on to the rack inside the bag.
Because this new material is so much thinner than the carpet, I'm going to need to put some sort of protective covers over the bolt heads.
MR: thanks for the mat, I decided not to put he bolts further outboard, as you suggested, because I didn't want to burn more bolt holes in the bag.
BTW, to make holes in the board bag I use a soldering iron rather than a wad punch because it seals the edges of the hole.