You can put anything in your log book that you want to! It's your log book. Heck, mine is nothing more than an aviation diary.

The FAA only requires a log (or detailed record) to document aeronautical experience required for the issuance of a certificate or rating under FAR Part 61 and/or to demonstrate recency of experience.

Prospective employer's, on the other hand, may or may not accept SIC flight time recorded in an airplane that doesn't require an SIC. In the past they generally have but with so many guys 'n gals on the street these days the prospective employer can be much more pickey.

TransMach