Hi OP, you could try to contact Allied Control (
http://www.allied-control.com/index.php). I know they have built and run a 1T+ mining farm using over 6000+ spartan FPGA with immersion cooling. But they have dissolved the farm a few months ago because of the difficulty and the ASIC miner.
I have not contacted them but still closely at their designs and their results, They use Novec 649 in some of their projects.
Yeah that is another option for working fluid. IIRC they used Novec 649 (boiling point of 50C).
I've been researching this product and is a different family of 7000, this is a
acetone that can break down the coating of the wires, we are studying other solution is to use the Novec 7100 has a voiling point to 61º and mix it with the 7000 to reduce it, this tells 3M is possible.