I just set mine up to fill from a thruhull with a hi speed pick-up/clamshell, which has a valve to regulate in the tank(also a valve on the sea-cock). The overboard is going through a 500gpm bait pump
http://www.tackletogo.com/shbase500gph.html that has a valve at the outlet to regulate flow. I have a standpipe that can be adjusted to set the fill level.
I have only tested the setup briefly, The valves have to be adjusted with speed, but I think it should work well for my needs. Also this is on a 18' and there is a drain fitting in the well that goes to the bilge.
