If you watch carefully the Terralux modified MiniMag, you will see it about 5 mm (1/5 of an inch) longer than a standard MiniMag, when it is off. It should not be so.
Also, the continuated ON/OFF operation by turning the bezel "erodes" the emitter and reflector, resulting in farke inside the reflector. (I have the NEW reflector). The problem can be reduced with some silicone grease around the Luxeon. Also, overtightening the bezel will crack the reflector.
The wobbling of the bezel, due to the poor machining tolerances of the Minimag, makes the beam pattern unstable. This is true also with the stock bulb.
On the opposite side, the Terralux has very low power consuption (300 mA), and runs almost cool.
Talking of the Minimag, the most professional mod I have seen is the Opalec NewBeam.
Regards
Anthony