My spoilboard is 3/4 mdf, 1/4-20 T Nuts on 2" Centers.
Made some clamps to hold things down, on the straight clamps I used 1/4-20 threaded inserts so I can adjust the height for different thickness stock. cheap and simple. Just noticed yesterday that reversing the height adjust screw in the insert allowed me to lower the clamp for thin material helped greatly.
About $12 for the 12"X12" HDPE, a few inserts, I am using allen head screws and some washers.
Happy to send the V Carve file to anyone interested