I'm not sure where they are most appropriate, but I tend to see them on formal dress pieces in yellow gold. The watches tend to be in the classic size range too - nothing above 36mm.
... or at least that's the association. The practice these days seems to be to use large, square scaled alligator for today's larger watches. Vintage watches seem to come with smaller, perhaps rounded scales (further away from the centre belly), perhaps because of cost, aesthetic or other reasons. I prefer smaller scales on smaller watches in any case - it seems to be better proportioned and balanced - ie small rounded scales would work better on your PLM than on a larger RL PLM or the ZW for example.
I think they'd look good with your PLM, also for the reason that they would work with the round registers and toubillion. Perhaps some before and after photos?