Impressive spreadsheet!

If I were the pedantic sort I'd remind you to add in the heat load from the pump, but I'm not so I wont ;)

The entry holes do look a bit piddly. Thin tube is more bendy (showing my full engineering acumen here) which may be a nice feature when connected to the moving head. I wonder how 12mm ID 19mm OD tube will fair after 2 weeks of constant bending and twisting?

The reduction in diameter sounds significant and may well be a design feature used to increase the velocity of the water over the cooling part:

1) Higher velocity means less laminar flow ie it minimises the occurrence of slower moving 'layers' of water near the boundaries which effectively 'insulate' the metal from the main cooling flow.

2) The common sense of many tell them that the longer the water is in contact with the metal, the more heat the water will take up, or give up if in a radiator. This is of course pants, in and out asap is the way to maximise the amount of energy transferred..... Unless achieving a satisfactory velocity requires a 200w pump ;)

Jet Plates!! Sounds good, lol http://www.thewatercoolingshop.co.uk...-HF-Plexi.html

Hehe, extra points to anyone who can tell me what the 'Blank' jet plate is for :)