[Miss_Man]

I think you'll have to sacrifice some clamping pressure if you want to direct water cool the pelt. I think the reason why pelts work so much better with high clamping pressure is because the many many little metal things inside that transfers the heat across dont have such good thermal contact with the ceramic plates to begin with. And with so many of them spread across the whole pelt, applying pressure just at the perimeter would not have as good an effect as applying pressure throughout.
That said, you have some rather spreaded out pressure with that chanel design so it shouldn't be too bad. Perhaps like they said, epoxy isn't such a good idea, but some form of insulative barrier should be implemented.
Perhaps you should have the shell with the same height throughout so that when the coldplate comes on, it isn't in contact with the shell. Then you can use screws to tighten. As for preventing water from leaking out, maybe silicone or plumber's goop. Actually what I'm describing is much similar to Tom Leuken's block except with your chanel design + forgoing the rubber gasket, and a cold plate clamped on.
All IMHO.