Solder? Epoxy? I used to have a real hard time with that one until I broke down and bought a nice soldering station... My Weller broke down years ago and I had been using a $5 Radio Shack special... It either wouldn't get hot enough, or would get so hot that it would fry components...
I have visions of that big inductor ripping off of the board after a few miles of rough road.
It really should be secured to the circuit board somehow. A little RTV, maybe? Make sure you use the stuff that's not acidic, as it eats way some of the copper.
Other than that.... If it's converting 3A of current, it's probably dissipating a watt or two. Wouldn't hurt to mount it somewhere thermally conductive so it can get rid of the heat.
I've used epoxy with a number of DX drivers (either directly to the body or to an L shape and never had any problems. I've also used the double sided adhesive tape from component shops (used on computer boards) without problems.
If you're concerned about electrical insulation you can always smear a thin layer of epoxy over the board and let it dry before attaching it to the body or bracket.
Artic aluminum is allegedly an electrically insulator so I could use that to connect the driver to the L bracket then connect the bracket to the body that should deal with the heat. You reckon some silicon between the driver and the inducer would be enought to keep them together.
Yes the Arctic Al products are good insulators and I used to use them to mount items like drivers once. These days I only use them to mount LEDS since I discovered that a thin layer of epoxy worked in most cases.
I ride a lot of rough trails on MTB and have never managed to shake an inductor off a DX board (almost all my lights are home made).
Regardless of your choice of AA or epoxy remember that a thin layer works better. The AA is not the heatsink and a thin layer will give more efficent transfer than a thick one.