Hi. I'm new here, though I've been using HO-fluorescent and MH-powered Algae Scrubbers for a long time (ever since I read the first edition of Dr. Adey's book a long, long time ago). I'm interested in making the switch to a compact LED design. I'm a bit stuck on some of the engineering aspects of designing an LED system, so I thought I'd ask for your advice on this topic. Specifically, I'm getting stuck on the thermal power dissipation calculations. Unfortunately, the suppliers of pre-mounted LED on the metal-core PCBs don't publish heat transfer ratings for their products, which means that there's no way to approach the heatsink problem mathematically. I'd like to avoid the approach of just taking a stab in the dark at mounting LED on a randomly chosen heatsink and hoping for a good outcome. Optimally, I'd like to know the specs for heat transfer of the MCPCB-mounted Luxeon Rebel ES, like the ones that you can buy from Steve's. My goal is to crunch some numbers to determine how many LEDs operating at full power can safely be mounted on one of several possible heatsink choices, while ensuring that the finished product will maintain an operating temperature low enough to ensure that Tj on the LED is still in the high efficiency portion of the Thermal Pad Temperature vs. Luminous Output characteristic. In the absence of clear-cut engineering data, it might be helpful to know anecdotal experiences, like: how many LED you were able to mount onto a heatsink; how much power they were dissipating; what the C/W rating was for the heatsink; and what was the observed operating temperature on the heatsink, using something like an IR thermometer. Hopefully, obtaining some solid data like this would help me to approach the problem from an engineering perspective rather than just taking a shot in the dark. TIA.