So, with insight from the two Scotty Facebook sites and NSSO web site, I broke down and bought the basic Dremel tool, and a set of metal cutting discs. Pretty slick, a small, hand-held (that's it in the first picture) high speed cutting/ grinding/sanding/polishing device with many other uses. Applied to the Scotty, with a 1 1/2 inch metal cutting disc, one can either "slot" the screw nails, or, entirely grind the heads off. And, with a bit of practice, seldom gouge the remaining "L molding" (or, fairly seldom).
Powerful little tool, that Dremel tool - use eye protection! Some of the screw nails were stainless or galvanized steel and most of the original ones were aluminum. The steel nails send a vast shower of hot sparks and steel shavings flying, and the aluminum nails create a blizzard of aluminum shavings/aluminum dust; so, eye protection is a must! Here are a couple of pictures:
At top left, me and my trusty new Dremel tool attacking those nail heads; are top right, several nails that (with the new slot cut) could be backed out with a screwdriver. Bottom left are nails with the "groove cut"; with some, a screw driver will back them out, with others, part of the nail head, or all of it breaks off. With the aluminum nails, it's easy to just grind the entire head off! Hopefully, this tedious grinding process will be finished by tomorrow, and, we'll be pulling those aluminum skins and roof panels to see what water damage, and fun, awaits!