Largejet,
Having just begun to see how I can keep my logbook consistent with being legal and safe you have raised another issue with the Tech Log although this must surely be less of a problem. Signing the Tech Log means you have accepted that the aircraft is in a fit state to carry out the intended flight. We usually sign the log after the flight to indicate any or no defects and that the aircraft has actually flown for the recorded time and been where you say it has.
Surely, in light aircraft you cannot have 2 crew unless one is Instructor and one is Pu/t