I think I'll do this mod as well. The TK15 IS NOT a good tactical light for me. The small button is almost impossible to get at quickly if you need to switch modes. It is only useful as on/off in a stressful situation. Still a fine all around light.
what's your solution?
Take hand off light and twist lens to change mode? Or tap the "momentary on" and have it change modes every time?
I'm like the TK-15, momentary or ON with my thumb, mode changes with pinky... all one hand.