E21 or TK20 for general use/weapon mount?

[RiverRatMatt]

I came close to pulling the trigger on the TK20 today - but I saw that without the rubber the grip is actually tapered
Using something as a spacer like I do with my L2D, would it work or would the taper slowly push the light forward? It'd be going on a 12 gauge Mossberg 500A.

OR, would a slightly less bright E21 be a better option? I notice it has a solid, grippy aluminum body, but would the light stand up to repeated firings on the end of a shotgun?

 

[RiverRatMatt]

Actually, I decided to go with the TK20. I actually think I'm going to use my L2D as my shotgun light