Don't bother overdriving a red luxeon. The performance degridation due to heat outweighs any extra light you'll get past 400mA. The red has a higher thermal resistance to the slug than a white does, and suffers much more from a high junction temperature too.
For instance, at Tj=80C, a red is only producing 60% of the light it would produce if the junction were at 25C. A white, on the other hand, will still produce 80% of the light as at 25C.
The Vf of a red will also increase faster than a white. I tested a red-orange at 600mA, and its Vf went up to 4V.
So, let's assume you want to run it at 600mA. Let's also assume you have a perfect heat sink to the star board (20C/W J-A thermal resistance), with an ambient of 25C
At 1W (350mA), Tj=25C, you would produce 44 lumens. However, your Tj would be 45C (25C + 20C thermal resistance), so (looking at the derating graph) you would be putting out 0.8 * 44 = 35 lumens.
Now, let's run it at 600mA. Your Vf will probably be 3.8V. Your junction temp will be 2.28*20 + 25 = 70C. Let's assume that at 600mA, you're putting out 1.3 times the light. So at Tj=25C, output would be 57 lumens. But, if we factor in a Tj of 70+25=95C. At 95C, output is reduced to 50%, so an output of about 29 lumens. By overdriving, you're actually reducing the light output.
