I have had my CNCRP for going on three years now and have had nothing, but good experiences with it. My spoil board has served me well and will need to be replaced soon. However, I want to see if I may want to look at alternatives for holding down material.
What I have today is a 1/2' MDF base with a 3/4" MDF spoil board. The spoil board has 4 holes in it and a grid carved into it to direct airflow from a shop-vac. Its not in the photo, but I have PVC pipe and valves to open and close each section when needed. This is he best shot I have from when I built it before dust collection was installed.
This method has been helpful when holding down thin sheet goods like 1/8" MDF, styrene, or foam. However, the bulk of the time I am cutting full sheets of 3/4" MDF and use multi-purpose screws to hold it in place. The shop-vac can't hold the MDF, not to mention it gets very noisy and running the Shop-Vac for hours on end is not good for it when there is little to no air flow.
Overall, I have been satisfied with what I have, but there have been times when a 49x97 sheet does not sit flat across the entire bed. Also, after a while you run out of places to put screws as the spoil board has too many holes in it. Not to mention, I am always scared I am going to hit a cross member.
What's your hold down method?
Thanks,
-Eric