[krazy]

Why not mount the heatercore flat on the bottom of the case and duct the intake air? This saves on drive space and makes it easier to get air out of the thing.

A reservoir is recommended over a fill tube because the tube and T fitting doesn't slow the water down at all, and the air can't get out of the system. With a properly sized reservoir, the water's velocity slows down enough that the suspended air bubbles can rise to the surface before the water is sucked back into the pump.

Having the res or fill on the outflow side of the pump (that's what it looks like there) will make it harder to fill the system. I recommend putting in right on the intake of the pump to make filling easier and also decrease the load on the pump's intake.