To quote Dan H, "in God we trust, all others must bring data".
Well here's your data.
I ran one of the lights (4,900 lumen Squadron Pro) with the vehicle off then running, and the results were as follows:
Engine Off: 12.2V, 3.65A giving a draw of 44.5W
Engine Running: 14.1V, 3.00A giving a draw of 42.3W
With the engine off or on there was absolutely no difference in the light intensity.
Thus it appears there are some fancy electronics doing their thing and ensuring that the light output remains constant regardless of the voltage. The only thing is that as the voltage drops, so does the efficiency of the light, but without sacrifice its lumen output value.
I also noted the AWG of the cables, and it appears that when running both lights through one cable, Baja Designs uses 18 AWG, then when they split the lights into two cables after the switch they use 20 AWG. I forgot to measure the cable length, but I'm guessing a run of about 10 ft (or 20 ft if you include the return ground) or about half what we are working with.
Thus, if you were happy with only a 1 volt voltage drop, which is half what I was dealing with in my test this evening, then the light would be drawing approximately 3.3A. For a 1A voltage drop you use chart 11.3 on page 11.31 of AC 43.13-1B, which results in a wire size of 18 AWG, which seems to reflect everyones previous experience with the lights!
The only thing I did note that was a bit of a downside, is that with the lights now installed in the tips, there seems to be a lot more diffusion of the lights because of the slightly recessed positioning, resulting in a reduction in ultimate range, but giving better taxiing lighting. For sure only get the spot version, as the diffusers are not necessary if using them in this recessed tip configuration. I think in hindsight I may have made cutouts in the leading edges and placed them in there if I was to do things again, or even use the larger XL 80 version if I can make them fit, which would about double my light output. I may still place an additional one on in the cowl (I need some nose weight anyway).
Thanks for helping me save 0.32lbs by stopping me go down the 14AWG path.
Tom.