How does everyone log time in your logbook as an FO while part of an augmented crew?

I've heard to log...
1) the whole flight as total time and SIC
2) the whole flight as total time and only time in seat as SIC
3) only time in seat for total time and SIC
4) a predefined ratio, log 2/3 of total and sic if 3 crew, 1/2 if 4 crew

Seems to be weird to be logging time while asleep in the back, but also seems to be weird to be logging only 4 or so hours for an ocean crossing.

Thanks guys