That's a nice looking table. Done right; large insert, more narrow track... What's that last pic? Tough spot. Not super tough though. The underlayment is an option. Seems to be spendy though. And the old foam wrapped the insert... Did you build this one? There's work involved in getting a new insert board. The foam will work for a new board even if it doesn't work on top of this board. I wouldn't worry about any space between the insert and the track no matter what you do. It should be small. I'm staying in the camp of trying this foam on this board. I get it, it's a quarter inch. Cut the foam, exactly, slowly, and precisely, maybe a hair (1/16") bigger all the way around and then when you cloth you won't see any space. It'll play fine. And nobody is going to have an issue with that quarter inch. Like I said, I like a little step up. Worst case scenario, you have to replace the board and redo all the staples. While the table is apart, I'd use some poly on the inside of the table that sits against the insert. It takes time to dry obviously but will keep the wear on the cloth to a minimum, erase any optics of the bare wood, and it's just the right thing to do. You won't see any of that inner bare but again, if I were you this is the route I'd go; try the foam and replace the board if you ain't feeling it.