Too thick, yes. Acceptable, yes.
As Mathias said, no one is going to tell you to replace it, so if you're happy with it, then stick with it.
By comparison, here's a couple of shots with a 3mm and a 1.6mm rail.
http://www.whitearmor.net/forum/topic/32111-fisd-e-11-blaster-reference/page-2#entry414706