DIY Aluminum block thickness Q's

Hey guys. I have access to a milling machine and am probably going to make a waterblock to cool my northbridge ( nforce2 fsb ocing haha ). So my question is, how thick do I make it? Do i model it after copper blocks or do i do something different?

It is amanual mill so I am probably going to just use a square spiral pattern. Let me know ifyou have any ideas. Thanks!

I can't see the northbridge putting out giant amounts of heat, so design should mostly be up to you.

Thickness wise I wouldn't want more than 3/8 between the bottom of the design and the NB core.