OK, thanks. That makes sense. I've viewed this several times, and debated asking, but my curiosity finally got the better of me. I think the suggestion Richard has made, is about as simple as it gets. I have a fairly large stash of mechanical drawing pencils here, with leads graded from 4H to B, so I can always find something that will work.
Also, as it turns out, I'm quite an avid (some might say rabid), aviation nut, with gobs of aviation references. If you should need specific photo references, please don't hesitate to ask, and I'll try to help out if I can.