many thanks, Travis, for your detailed answer!
the last question can easily be answered:
a "Thumbnails" preset should never clobber an existing one,
only on "fresh" creation.
meanwhile I've played a little more with the thumbnails,
and all the white/grey from my previous posting burns my eyes now...
I've resorted back to the thumbnails settings I had used on the previous system:
bgcolor = rgb(251/250/230)
default = rgb(211/211/211)
the last question can easily be answered:
a "Thumbnails" preset should never clobber an existing one,
only on "fresh" creation.
meanwhile I've played a little more with the thumbnails,
and all the white/grey from my previous posting burns my eyes now...
I've resorted back to the thumbnails settings I had used on the previous system:
bgcolor = rgb(251/250/230)
default = rgb(211/211/211)