Essox - Can't help you with the specifics (my Pro Crappie has 2 baitwells and we love it) about GPH or pumps, but I would suggest you build it OFF the front casting deck (which is what I think you're planning to do). The reason is mine (check out the catalog or www.trackermarine.com for the layout of my boat) is located on the right side actually on the front deck and takes up a decent amount of space. Granted my son loves the play with the minnows, but if they had make the livewell infront of the console bigger to accomodate the bait well (like they do on the Panfish 16) i'd have more room on the deck and the bait well up front.
In my old John boat I just bought a small cooler, added a 12 volt spayer-type airator from Academy (in TX) and wired a plug/recepticle into my boat so I could take the cooler out to clean or fill up with bait.
let us know how it turns out and we want pictures!