Kevin,
You could look for an oval poly tank to fit inside a glass outer box. Find a small rectangular fiberglass utility/dock box. Foam the oval tank in to the glass box for stability. You will prob need to raise the leaning post/backrest above the box on custom aluminum tubular posts. Daggone those T-Top shops.... :)
I have a similar built-in on my '95 Pursuit 2470 CC. Good arrangement, seat/backrest above an oval tank, but this unit was part of the liner, and not going anywhere.
Thing is, you want some confidence in your design/engineering. Make sure what you end up with is overbuilt for the job, stable, part of the boat. That 40 gallons of water weighs around 300 lbs, and its up on the deck. Keep the plumbing internal (like the Hammerhead) so won't be tripping over that mess when the fishing gets to catching. And make sure you're outlet size(overflow) is at least 2X as large as the intake; i.e., 3/4 in, 1 1/2 out, or more.
Safety note: Many boats have sunk due to poor livewell engineering/maintenance. MAKE SURE to have quality ball-cocks above thru-hull fittings, inlets AND outlets. Why outlets, that seems unnecessary, right? Almost sunk my 1979 2100CC Hydrasport 25 years ago, while offshore by myself. The 1 1/2 in outlet hose failed (split) , and the water continued to pump into the aft below-deck livewell. Noticed the boat got heavy; found the problem; shut off the pump, and the inlet seacock; but no way to shut off the intrusion flowing by water pressure from BELOW(seawater) in to the 1 1/2 inch outflow, due to the breach. Was lucky, got it up on plane, and ran the bilge pump home. Ran the boat straight to the ramp and trailer. Very lucky, very fortunate. And this was Hydra-Sport factory rigging, circa 1979.
Have checked the Hammerhead site, since I've been been hunting an old Aquasport for a while. Spoken with them, too. I don't think they're out of line for what they produce. And wow, I'm pretty impressed with their stuff.
They advertise that livewell/seat for 800 bucks. Its a beauty, heavy acrylic lid, blue gelcoat interior, baffled, finished, all internal, hidden plumbing. My luck would be I'd try and duplicate it, and the whole mess would wash out in a heavy following sea.
You could whiz away 600 bucks trying to duplicate it, or go ahead and spend 200 more, and have something THEY are responsible for, or at least have onus to. Just a thought.
Best, keep us posted.
