Got an idea for a gaming mat

[Smokeyrone]

Saw "Carpet Cushion" at Home Depot.   Not the old skool stuff, that is cheap, pressed spongy pieces, this is a roll of 1/2" thick rubber foam, that is just heavy enough to lay flat on a flat surface (I tested it, 8 feet from a roll layed flat).   A perfect storm of weight, texture (smooth), strength, etc.    99 cents a square yard.

Seems like a great medium to cover in paint, sprinklle on fine sand and such, overcoat with paint, and use as a base mat.   

The issue is will it warp (curve upwards) after painting and finishing?   Even though it looks like the best material I have seen, I have to think it will.    So?   Figure out a way to secure the corners down flat on my table.   I'm thinking a carpet tack in each corner.  That would do it.  IF warping is an issue. 

I am done with foam/wood/whatever "sections/tiles" of 2x2, 2x4, whatever.  I HATE the lines between tiles.   

Anyone try this?