Tom,
I believe the 30deg guideline is for circling around an object. Such as moving and capturing around a statue.
If you draw a circle around the object and mark the camera locations, it should look line hour marks on a clock (30deg into 360 => 12 shots). While that may be a good rule of thumb for minimum alignment, I would recommend doubling that at least.
The 80% overlap is more for moving along a wall or something similar.
Basically these rules are the same thing; designed to ensure that sufficient visual information is maintained between adjacent images. It’s just that one is designed to help with moving across walls/etc and the other for moving around things.
Regarding the 8mm fisheye lens: I think it’s somewhat counterproductive :)
While you do get 100% overlap, that also means that “pixel resolution per feature” is worse. Keeping all other things constant, as the lens gets wider, pixel density per cm gets worse. Which means less stuff for RC to “see” as features. I’m guessing that’s one of the reasons why your fisheye experiment resulted in poor feature count.
This would be particularly bad for plaster walls and such. Those actually do often have a lot of small features, especially old walls. But if you aren’t “zoomed in” enough, all the little bumps/cracks would be effectively lost.
Regarding your D60 + 18-55mm example: I didn’t quite follow your math. Not saying it’s incorrect, I just didn’t verify it :). But I do think you are convoluting the angular rotation vs lateral movement calculations.
For a zoom lens, I think it makes sense to set it to one extreme or the other (18mm or 55mm). That way there is less chance of slight zoom variations during camera movement. Unless you have a zoom-lock lens.
(There is an added fun fact that these kit/zoom lenses are usually not the sharpest at highest/lowest zoom, but should be OK at f4 or smaller)
Anyway, set you lens to 18mm (or something else if necessary). Given the distance from the wall, figure out what the field of view is (how much width of the wall do you see). So if you see 5m of the wall horizontally in your image, move 1m (20%) to the side. That’s your 80% overlap. Same thing for vertical