Perhaps it'd be easier to use some sort of band clamp? Like a pipe clamp, but specifically designed to clamp the light bracket to the fork. That'd also make it easier to move it up and down the fork to get the best position.
As an aside, I've found a headlight modulator works wonders for getting cager's attention. It's saved me many times from a car pulling into the roadway in front of me from the right hand side. And when you're threading the needle, that flashing headlight tends to gets the attention of the cars so they know you're coming up alongside them.
I've got a Kisan Tech P75W PathBlazer Headlight Modulator. It'd designed for incandescent headlight bulbs, but it works just fine for the newer LED lights that don't have the little LED driver box, and as long as the LEDs draw enough current to trigger the headlight flasher.
Here's the headlight I use, a 30-watt 6-LED bulb:
http://www.amazon.com/dp/B00PRW2KJK/2x High Low Beam H4 9003 HB2 720LM Xenon White 6000K XBD CREE 6-LED Headlight For Car
I like this one, because it attempts to emulate the light coming off an incandescent bulb's filament. It does this by aiming 3 of the LEDs backwards toward a rounded reflector surface that then reflects the light onto the bike's OEM reflector. The other 3 LEDs face forward and go through a focusing lens, for the high beam.
For conspicuity toward the rear, I have the Kisan Tech T50W TailBlazer brake light flasher, which flashes the brake light when the brakes are applied.
I also recently bought a license plate carrier that has 12 red LEDs in it. It sits behind the license plate and puts a halo of red light around the license plate. I'm going to wire it into my brake lights, so when I hit the brakes, my brake light modulator will flash the LEDs. I got it from InterstateCycle.com / KymcoPartsMonster.com. It's usually $59.95, but since I had some Interstate Cycle Dealer Loyalty Points, it only cost me $7.98. If I find it's not bright enough, I'll rip it apart and solder in some *really* bright LEDs.
In addition to that, I have the reflective rim tape on the wheels, yellow on the front, red on the rear (colors required by state law).
I also replaced my position lights (those two small lights to the left and right of the headlight) with LEDs... now it's like I've got 3 headlights, those position light LEDs are so bright.
W5W 501 T10 5W 5 WATT CREE LED Wedge Car Light Bulbs - Xenon White
And of course, my brake light and turn signals are all super-bright LEDs, as well.
Brake:
http://www.kymcoforum.com/index.php?topic=11926.01157 High Power 5630 Chip Cree LED Red Turn Signal Brake Tail Lights Bulb
Front turn:
http://www.superbrightleds.com/moreinfo/s-series-bulbs/led-product/527/BAU15S-x18-T:18HP-LED 7507 (PY21W) LED Tower bulb - BAU15S-A18-T:Amber
Rear turn:
http://www.amazon.com/Jtech-BAU15S-Power-Yellow-Signal/dp/B00C16FS1CJtech 2x 1156 BAU15S 13W High Power LED Yellow Signal Light
License plate:
T10 Wedge 5 Ultra Bright SMD LED Bulb
http://www.ledlight.com/t10-wedge-5-ultra-bright-smt-led-light.aspxI also want to install supplementary lights like you're doing, but I'm not sure it's legal to do so here. Gotta do more research.
