Why would quad concave give you pop? Seems similar to a tri-hull design... smoother ride because it breaks up the surface instead of skipping off of it. But it also means more drag because there is more surface area (although not much more so this may be insignificant).

My understanding is that pop comes from loading up the board ... there is actually a formula I picked up from the board making group to calculate how much pop a board design will have. The inputs are width, length, and flex.