Sinewave USB/Lumotec Fly light pairing question
 

I have a question about wiring my Sinewave Revolution USB charging device from my Shutter Precision PV-8 hub, in conjunction with a Busch and Meuller Lumotec Fly Senso Plus light.

Specifically, where to tap into power to supply the Sinewave -- directly from the dynamo hub, or from the power-out tabs on the Lumotec Fly headlight. The Lumotec Fly Senso Plus headlight has two sets of negative/positive power-output tabs on the back of the light. The owners manual tells what to do with only one of the two sets of power-out tabs. One set is clearly labeled in the user manual (the bottom pair) for powering the dynamo LED tailight (I got the Toplight Senso Plus tail light). The owners manual for the Fly headlight says nothing whatsoever about what the other power output tabs are for. I assume that they are a handy connection point in case you want to run a pair of the headlights (don't know why since the Fly is so darn bright on its own).

I emailed the Sinewave Revolution makers and asked if I could use that upper pair of power outlet tabs on the light to power the Sinewave. But they told me that I should run a second set of power wires directly from the hub and directly into the Sinewave. I questioned why this would be advantageous to using the spare pair of output tabs on the light, and they did not give a clear reason, but stated again to tap power directly from the hub.

I do not want to run any more wires than I absolutely have to, since I want to keep my ride neat and tidy. However, I do not want to make an aesthetic decision that creates a power problem for the Sinewave.

I know that it is recommended to use the Sinewave to charge USB devices only when the headlight is turned off, so that all of the hub's output power is available to the Sinewave. I can switch the light off and the power outlet tabs from the light still allow the power from the hub to pass through the light circuitry without illuminating the light.

So, two questions: First, what could be the harm in tapping the Sinewave into the spare output tabs of the headlight, instead of directly into the hub. Second, does anybody have any documentation that describes what that spare pair (the top pair) of power output tabs is intended for and any limitations on those power output tabs at the light?