Im not sold on bottom position (er I mean....).
Truth be told Im thinking front right rail.
Ive got a class in January, nother in May, where I will play with location on the light.
Shooting the other day for "precision" shots I was using a roof column, left and right side, for support so bottom of the rail worked than.
Actually working the light its a little easier when on the front of the right rail. I am a right side shooter so my support hand can bump or flip the switch. I think when I got home and went through my rail covers/messed with my sling I may have moved the light back to the right rail.
Im messing with how I run my sling. Right now I QD to the front of the left rail than QD to the right side at the SopMod stock. Again only class time will tell me if that works.
Interested in hearing what works for others.