I agree on the flashing during daylight - front and rear. I also found
that 12V systems with a external battery are the brightest and worth
the extra weight (3-4 lbs). Battery sits in my rack bag.

I have pictures (jpg) and two short movies (mp4) of my lights during
daytime at: http://gto.johnsoncityphotos.com/

You will see in the photos the dual flags that I use for visibility. I
don't ride at night, but then the dual lights are amazingly bright.

Good luck on the light choice.

73/gus