I just guessed on the accumulator volume. 2" PVC x 100" (4 @ 25").
I have zero leaks in the system right now when using a small gasket between the platen and a piece of candlestone as in the video.
I do leak when I use a MDF spoil board. So much so that it will not hold a true vacuum. Even MDF sealed with 2 coats of poly leaks some. More tests in this area will need to be done for sure.
The system has a vacuum controller in it that is currently adjusted to about 22 in Hg and will auto cycle the pump to maintain that level of vacuum in the system. As long as I don’t have any leaks that are massive (like a MDF spoil) I should maintain vacuum clamping with relatively minimal pump running time.
The key now will be in the design of the spoil/holder boards. I will probably look to make these purely out of HDPE or starboard or some similar non-porous material.