Thanks to all for the various reactions (including private comments
from Eric Fergusan and Sophie van Leersum) and the interesting Foss
threads ensuing. A mathematician myself, like Hugh Foss, I care about
details of the deviser's intentions, when they are available ...
Ian Boyd's answer settles the query about Wee Cooper, as far as I'm
concerned; given that it's definitely lead down crossing over in
bars 7-8, using left hand is natural starting from the opposite side.
Although it seems obvious, I wanted to check because I heard that
sometimes people use no hands, i.e. 7-10 becomes a half figure of eight.
Unfortunately I am still in the dark about Earlstoun Loch, since the
Scottish Dance Archive sheet (freely available on the internet)
doesn't go into sufficient detail. For now, my working hypothesis is:
23-24, dancing couples lead up, turn towards each other and continue
turning to face down
25-32, all do maximum turns using pdb ;)