If your opspecs call for another qualified crew member then you had better be trained to be a qualified crew member or your company is in violation, that said not all 135 operation require a second crew member take Cape Air for instance they operate single pilot as long as their auto pilot is not MELed, are there operators allowing CFIs to ride right seat and log time perhaps but I suppose it was on the 91 repo flight as long as the PIC is an MEI and is giving instruction the right seat time should be logged as DUAL GIVEN I don't think that MOST 135 operators using King Air type a/c would risk the insurance liability.. if you KNOW of some of these operators doing other wise do you want to share if its your belief that that kind of practice is wide spread I would hope you would alert your local FSDO if you think that the operation is shady and possibly a safety problem for the airspace which you operate in. Thoughts....