I'm thinking I'll put mine farther down on the tang to get it close to my eye.
I've wrestled with that as well, and spent an inordinate amount of time with a 48" long 1x2 board, with a nail on the end and varying placement of a small diameter washer, deciding where I wanted this thing to go.
And I may still move it back some - haven't drilled yet.
Placing it where I plan is #1 an easy drill job, #2, provides the shortest stem length, and #3 - will be easy to fill if need be.
Of course, there is always something along the lines of this, which is easily adjustable to distance from eye, although I probably wouldn't put in the adjustments with the knobs.
http://4.bp.blogspot.com/_j7PMWDJke...jo/s1600/Billinghurst+action+closeup.bmp 
