You don't need a heatsink in my experience. Never used one myself. I have a MCP355 from 2008 that has over 40,000 hours on it no problem. Recently I've been using this L-stand, and it's what is holding the pump in my picture on the previous page:
http://smile.amazon.com/XSPC-Acryli...pebp=1437060564313&perid=1D62J1GC5N2NVR7FK4Q4
Keeps it out in the airflow and provides and easy mounting method. I just drilled four mounting holes for it near the edge of the motherboard tray in my 900D.
I think you're fine with 1/2" tubing. The tubing adds practically no resistance or PSI drops. It's the blocks. I run 3/8" personally, but that's because I never had a need for anything else.