I bought a Luxeon III 3 watt LED module for the headlamp of the S7 as an experiment. Its rated at 0.65 Amp at about 80 lumens. The viewing angle is decent too, so there's plenty of dispersion. I mounted it on an aluminum heat sink and mated it with a LM317T voltage regulator. I had planned for a current regulator setup, but the voltage regulator was more practical making the heat sink the Vout terminal and bolting everything together. I turned it on and got a faceful of light. It got rather warm after a little while while I was monitoring it with an RTD strapped to the heatsink. The rated max is a whopping 80'C... which I never reached set at half an amp draw, so I should be good.
I was rather impressed that it threw as much light as it did. The beam is a bit concentrated, but I think it may be enough to see with. I'll have to try it out. I'll likely never take the bike out in the dark anyway, but its nice to have enough light to be seen in the daytime.
The load on the dynamo is now perfectly attainable at normal running revs.