I am considering getting some new molds, and since they don't come with followers, I was thinking about ordering some of the "cutting board material" to make my own. I'm not sure what thickness to get. I don't want to waste my money getting it thicker than I need, but I want to ensure that they won't warp under pressure. I know that the larger the mold, the thicker follower I should get, but other than that, does anyone have any guidelines for thickness of a follower?