for a hold down i was thinking plexi top that would apply pressure only in the center.
EDIT: i was in a hurry before, might not have been clear what I meant. i mean a thick plexi plate with holes for four mounting screws and clearand holes for the barbs, and some mechanism that pushes on the wb in the middle (over the cpu) so as not to bend the base. I will also be using a shim with my cpu, so as to help prevent this possibly.
about the pumps - look here
http://www.aquatictech.com/pumps.html
max height for model 7 is 13 feet. 120 gph at 10 feet
at anywhere from zero to two feet ( which is about where i'm at) it quotes 550 to 700 gph.