Just curious, why would you want to put some foam under the seat? I assume you mean to lift the seat and put a block of foam there. I can't understand what it does, I have a Matrix winder tray in mine but used to put keys and wallet in there.
OK, if that's what it is then i understand. Middy used to sell it, haven't seen it for years though. These days, I carry pellet wagglers in a tube and 10-15 straight / insert wagglers in a box drawer. Modern paint jobs are much better than they used to be and they don't chip like they used to.