Av8tor, thanks for the vote of confidence regarding the positive stop. Yes, I completely forgot to mention piston dwell and as you mentioned, it can be quite a few degrees and it only increases as an engine ages and bearings get more free play. Commercial positive stops are available for nearly every size sparkplug and of course for engines with removable heads such as automotive applications.

I chuckle a bit when I hear someone say their timing is adjusted to exactly xx degrees then they quite a method for finding that number that had multiple posibilities for error. Still probably good enough for our simple engines.