I decided to do the collet lock cutout mod posted by @Sisco and now my Dewalt is a good inch from the wasteboard, using an Inventables engraving bit, before the Z axis V-wheels just slip off the vertical makerslide rails. I’ve come to the conclusion that we’re just going to have to stack up a few pieces of 1/2" MDF, get a flat end mill, and take off 0.1" across the whole thing to make a raised sacrificial wasteboard. Beyond that, try opening the mount and dropping the Dewalt a half inch?