I'm going to make my own version of the Incra Miter express sled for my table saw. My plan was to go with something like Baltic birch but I've found a cement supply store that carries MDO (also called sign board) for about the same price. Is there a downside to using over regular plywood? I would think the MDF faces would resist chipping and impacts better than birch. Also being very water resistant if something bad was to happen it could get wet without being damaged. It's been decades since I used the stuff but I remember it being very flat.