That article I cited above in post 17, I just looked at the drag graph. At 20 km/hour with light turned off drag was 1 watt, with light turned on drag was at about 5.4 watts. I am citing drag numbers for the PV-8 because that is the hub I use. (They did not measure drag of a non-dynohub wheel for comparison, so I have no clue if that 1 watt is actual additional drag increase for the dynamo or not, perhaps a regular hub has a 1 watt drag?)

They say that drag of 5.4 watts at 20 km/hour was equivalent to climbing 6 feet of elevation per mile. I am not sure what weight of rider and bike they are using for that calculation. But assuming that is accurate, at 20 km/hour, that is a bit over a foot of elevation gain per minute of extra effort. If you double that for your Forumslager, I probably would not notice that additional drag either.

The text in that article text:

"Electrical output is monitored with a 12 ohm resistance, since
that’s how it’s always been done, as bulbs are also
resistors. But LEDs are diodes, and alternators naturally
perform much better with those, especially if both
components play to their strengths. Actual power
output may therefore be significantly greater when a
generator is used with matching lamps."

I would take that to mean that drag is going to be proportional to hub output, but with some extra inefficiencies added in here and there.

Send me a private message with your home e-mail address and I will e-mail that article to you.