How bad would it be to just use the 10mm board and center it best you can? Why do you need to use a 16mm board? Is it just for better heat transfer?
I too am late to the Nichia bandwagon and need to get one (or ten) ordered up. Thinking to emitter swap one into a Trustfire F20. Glad you chimed in on yours apt323!
-Garry
P.S. Like your new avatar JohnnyMac. Is that a self-portrait? :) jk jk