I do not consider that an accurate method to compare efficiency - you should measure wattage in -v- wattage out rather than just speed (which also differs on wheel size, tyres etc), however that being said, I'd be up for comparing against it.

The D1 would track the pink line or better (I know 3W at 12kph is possible with a 700c wheel) but I've not ramped up the load at this speed to get the max wattage. Maybe it would be the same, maybe it would beat it. It certainly wouldn't loose, I'm sure of it.

Feel free to send me one and I'll add it to the database. I'll send it back for free. schmunzel

D1 max amps out is 3A, but I guess the dynamo in this test was fully saturated.

The only way to gain further efficiency is using mosfets on the bridge rectifier, but these pass current both ways which can interfere with any device which does frequency detection (i.e B&M rear light that goes bright when you brake). D1 also has frequency detection to prevent pulsing so this method couldn't be utilised.