I'm pretty sure you can't log copilot on anything other than a certified two crew aircraft, e.g. B737 except where an operations manual requires two pilots for a single pilot certified aircraft like a B200. For other operations e.g. C404 'two crew' there is the PIC and a safety pilot, but that is not a copilot.
Logging copilot on anything like a light single would be looked at suspiciously.
By all means, go for a ride with a more experienced pilot but don't put it in your logbook unless you are the PIC or are under instruction in a dual operation.