That’s a good idea to secure the sheet with two posts close together. I was going to secure sheet with At least two posts, but on opposite sides of the playfield, thus not allowing for expansion/contraction

In terms of expansion/contraction, I was going to do pretty tight cuts around posts ect so the protector looks more invisible, I don’t mind taking everything off, would thermal expansion be an issue with about 1 - 1.5mm post clearance if the game is always inside without huge ambient temp fluctuations?