Not to argue, but I can see the double row rivet line at "5" just as clearly as I see the one at the bottom of the 'patch' - plus can discern a suggestion of a faint shadow along the bottom of the lower double row where the skin lap well might produce such an effect.
I believe your impression that "5" is not at the right height is an understandable misread - it is easy for the eye and mind to resolve things a bit out of scale for their own subjective reasons. Consider, for one, that the reason the lower double row may be more visible is the shadowing along its lower edge - that adds emphasis that the upper row ("5") does not have.
I agree that I do not see the single midline row (between upper and lower double rows) you point out as not visible - unless I look between stations 331 and 343 on the Purdue site at the 'original' - there it becomes faintly apparent. It is true that this one is faint or disappears, although "2", "3" and "4" are single rows and are visible - their being in somewhat more favorable light possibly being the reason. The midline row, being a single row, also lacks the bulk of the double rows - but it also suffers from lying in a less favorable light plane, I think. The double rows in this area may have enough mass to make up for that loss of favorable light just sufficiently to be seen, whereas the single row may simply not quite make it.
I can also easily see another longitudenal single row below the patch / below the lower double row, between 298 5/8 and 307 - a slightly different area, of course - but low and not up in the light that tends to highlight the other higher areas.
I agree that I do not see rivets along the face of the patch, possibly for the same reason you suggest, or possibly because they aren't there. If they are there and are discernable, it is beyond my reach to detect them - and the same reason as for the midline single row may well be the reason. If anything bothers me about that, it would be simply that there are more rows on the artifact - 4, in fact, so out of those 4 perhaps a line or two might emerge? But I can't say that any one of the four would with any certainty, of course.
And as you've pointed out before, we're not experts at this kind of analysis, so perhaps we're missing something anyway.
That said, many of the rivet lines that do show up clearly enough can be validated as corresponding to known L10 structure; in that others do not where we know they must be is also, as you point out, somewhat telling about expectations for other locations in the same plane of light.
As to the Darwin ramp photo -
This particular picture remains vexatious to copy effecitvely: it is a bit grainy and light seems a bit scattered and much can be lost, I've noticed, even when working with a high-quality copy in tiff format if not careful. My belief is that more can be seen if it is simply
viewed directly at the Purdue site, and not at much enlargement at that - much over 50% starts costing noticeable detail. But, if a high-quality copy - like in tiff, is made at around 50% enlargement, contrast can also be sharpened slightly to bring out some detail as well.
Just for fun while we're gazing -
I have found, as an enthusiast, that it helps to study this photo and others like it as an astronomer might study the faint heavens at night - with
'averted vision'. Allow the eye to relax and not stare directly at the chosen detail, and much information can be realized and resolved than by trying to enlarge and pinpoint things among the pixels. Simply enlarge and soon you're chasing lots of tiny, false images. That 'star gazing' technique may work for some, all I can do is suggest it. It works well for me. Soft ambient and screen lighting helps.
I've used that technique a great deal since learning it as a boy to great effect in many situations, including this one. It's not exactly a science, and the results of course can be quite subjective if one is not careful - but it's an interesting technique and one might be surprised at what one can discern. I suggest avoiding the cloud bunny effect if one goes down this path - it is exceedingly easy to see what one's mind wishes to see if not careful.
