Nothing wrong with self made machines Robert.
Looks like you have rounded the tops of the letters which would suggest that your motor tuning settings need adjustment. Try increasing the acceleration and reducing the velocity (small adjustments each time and try the result). Reducing the overall feedrate may help. The problem would be sorted by operating in 'exact stop' mode (general config - select exact stop as opposed to constant velocity) but this would slow the progress of the overall work quite considerably.
Something else you may be interested in is this online utility for scaling GCode.
http://www.eng-serve.com/cnc/gcode_scale.html(By scaling 25.4 it will convert mm to inch).
I think we probably all learn by tweaking everything until it can be tweaked no more.
Tweakie.
btw. Good work on the HD logo, it's early days yet.