I'm going to be flying freight in a Caravan this weekend and am going to be taking along a buddy of mine. Two 91 legs and one 135 leg. I planned on giving a little instruction on the 91 legs covering systems, procedures, and aircraft familiarization. No problem there, but here is my question: Is it possible for me to give instruction on the 135 leg of the flight? or is this prohibited in the regs? I would obviously be acting (and logging) PIC, and he would be logging PIC as a student that is appropriately rated. In case you are wondering, the company is allowing my buddy on the flight as a "package handler".