Just spotted a DD-5970 in Crossfire build log over at Overclock.net !  Check it out when you get the chance!  He reports temps to be under 50C while running Furmark for 30 minutes!

System Specs:

1 - Core i7-920 @ 4.1Ghz using Enzotech Sapphire block (1.37 Vcore)
2 - HD5970 in CrossfireX using DD-5970 blocks
1 - 750ml Resevior w/flow meter
1 - Swiftech MCR-320 radiator with 6 fans (push-pull)
1 - Swiftech MCP-655 Vario pump at max setting

The room/ambient is generally about 22C , the cards at idle are at 27C , cards under 30 min FurMark stress reached 49C on the hottest gpu, VRM's 35-40C . The CPU idles at 40C and Max's at 66C under prime95 blend.

Radiator -> CPU Block -> GPU 1 -> GPU2 -> Pump -> Reservoir

Also noteworthy is the fact that these blocks are less restrictive then the previous GTX285 blocks I had from you. Flow increased approx 15% with all else being the same and only swapping the blocks.