Derek Cohen (in Perth, Australia)
David, what you are doing takes my breathe away. My offerings of what I use are really just a reminder to other mortals that there are pencils for purchase that work well.
The downside to ALL pencils and lead holders is that the pointy end rounds off, and this leads to inaccurate markings. Sharpening is one of those habits that is suited to someone less lazy, or less hyperfocussed on the task, that I. The 0.5mm lead is so fine that it essentially never needs sharpening to produce a fine line. The problem in the past has been that these blasted fine leads generally break after one or two strokes, and usually in the middle of a line. The Zebra Delguard is the first (and perhaps only) make that does not break. In part, the design of this propelling pencil is such that it has a shock absorber for the lead. In part, the lead itself appears stronger, less brittle.
Keep going with your work. It is fascinating!
Regards from Perth