I'll use US, USL, USR, DS, DSL, DSR, CS, CSL, CSR and then for 'inbetween positions', a format like: 'SL of DSR' rather than 'SR of DS' because the first is
clear that you mean a position between DS center and DS right, the second could be interpreted to DSR by accident. I think the craziest
blocking notation I ever used was something like "circles USRofCS clockwise starting at SRofCS" - yay for crazy moves
Notation is very much a personal thing though, diff'rent strokes and all that
PS: I have also seen SM and OSM used instead of PS and OP