The only way the pilot in the right seat can log the time is if it's dual received, they are the sole manipulator of the controls, or if they work for a 135 operator where the operating certificate specifies a need for two pilots.

I did answer the question. Insurance requirements mean nothing in terms of what can be logged and how. If the aircraft doesn't require an SIC per the Type Certificate Data Sheet or operating certificate you can't log SIC.

Since we were talking about Jetstreams, here's the TCDS for the 32. Min Crew is on page 3 http://www.airweb.faa.gov/Regulatory...%20rev%207.pdf