I fly in the UK and our OM let's us FOs log PICUS under a couple of conditions when PF. I logged PICUS until I had logged 150h of it and then stopped, as only 150h of it can be counted towards ATPL issue. I (as MJ suggested) have it hacked into a seperate column in the logbook.
As I side note, I have just had a look through CAP804 and the restriction for the max 150 PICUS hours seems to have changed.
LASORS used to say:
(i) 250 hours Pilot-in-Command (PIC) of
Aeroplanes, can include (ii);
(ii) 150 hours (max) Co-Pilot performing under
the supervision of the Pilot-in-Command
the duties and functions of a
Pilot-in-Command (PIC/US).
CAP 804 now says:
(2) (i) 500 hours as PIC under supervision; or
(ii) 250 hours as PIC; or
(iii) 250 hours, including at least 70 hours as PIC, and the remaining as PIC
under supervision;
So at least I can still fulfill option (iii)!