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On tankers we often went overseas with a crew chief in the sixth seat. Over in the States, for example, it would all be first name terms. Also, with the crew possibly sharing 3 hotel rooms, one guy would share with the crew chief and no-one thought this was a problem.
Back home, down on the flight line we would revert to "sir" and "chief" once again without any problem or resentment. Seemed pretty simple to us.
As an ex Victor Crew Chief I concur with TTN's comments. Never really had any problems. Back home some of the crews might use my first name, others would use rank - didn't bother me either way. We all new the system.
...and it often depended on who else was in earshot.
It was the same with ex colleagues who had been elevated to Hofficer status - just use rank it saves any embarrasment.