Randy at Phantom can correct me if I am wrong, but I would assume that just like any auxilliary light it doesn't make much difference. Some IR cameras even have a built in mounting bracket right on on top and the add-on brackets usually allow for a distance of 3 to 10 inches depending on the design.
You are illuminating an area in front of the camera so as long as the camera and light are aimed in the same direction I can't see where you can have it too close or too far away.
Great reply Wes... Also Wes i will be adding new handles to the site soon. They will be able to connect to any standard threaded camera/camcorder or bracket for way cheaper than that 40 bucks! They are super light and strong keep a look out for them.