What is the thickness of the Tolex? So it's the space width + Tolex thickness + a fraction to allow for a gap. You'll want to allow for a small gap between the Tolexed panel and the side wall just to insure against any audible vibration. I use thin shims when I set cabinet panels to evenly space a tiny gap for this reason. You can secure it tightly at the faces, but the edges are a crap shoot if you don't set a space or fit it tightly. A space is easier to do since it can be off a little without much consequence.