Quoted from Jean-Luc-Picard:I have seen people trace and cut out the "wells/arch" or "outlines of the objects" on the speaker panel.
I wound up drilling holes, then cutting out the outlines of the three treasures with a coping saw, and then used a Dremel tool to smooth the outlines. Installed the ColorDMD and the Marco jackpot light PCB at the same time and the game looks great. (I did shield the PCB from the ColorDMD panel like you suggested.)