Hello Pilotbro,
You cannot log any hours as PIC as an FO or SFO unless you are the aircraft Captain. This is just the nature of multi-crew operations. If you need PIC then you should try instructing, which can also lead to some aircraft positioning,charter work etc where you are left to make the PIC decisions and can log it appropriately.
A lot of the FO/SFO logbooks are full of P1u/s which is quite frankly a bit of a farce and HEMS employers know you really haven't been actually making all the P1 decisions on all of those flights, (as the Ops manuals state, and I think one of the big 3 operators in the UK state you cannot log more than 50% or something of the flights , with strict stipulations when you do) but a lot of pilots just log it and a large number of Captains, (wrongly) sign the books as they are not bothered, or don't know the rules?
Hope this helps,
B.