In most EASA countries,
PICUS is ONLY POSSIBLE when the Company has a proper programme for PICUS training, and APPROVED by the State of Licence.
For example, in Belgium,if you would write your PF as PIC(US) and they check your logbook, you can rewrite your whole book with the PROPER APPROPRIATE hours, meaning, if you are an FO, YOU ONLY LOG COPILOT TIME, you are NOT PIC!!!
You will also be told off very sternly and be considered a cheater by the authorities. beware.
If you ever change jobs, lots of airlines will just throw away you application when they see all your PF hours as FO written down as PIC.
Anybody trying this trick in my company is in serious trouble by the way...