Diver0001:
Why are you escalating this? Just use their rental gear and get the course done.
Sheesh.
R..
From a students point of view. When I frist started training, I looked not only to the DI but the DMs for examples of bouyancy control. If the OP has dialed in his buoyancy control, trim, and in water attitude using the BP/Wing, and there are differences in how ones dives a jacket BC vs. a BP/Wing, then to ask him to undertake a course as difficult (or so I've been told it is a challenging course) as the DM course in unfamiliar gear, for what appears to be no more reason than the DI's personal biased attitude, is ridiculous.
If the OP had dialed in his skills using the BP/Wing, than there should be no reason to ask him to switch. If he can demonstrate the skills that the DM is supposed to in his BP/Wing, then there is really no logical reason to make him switch.
As to the whole, boss pays the empolyee so the employee should just shut up, well that works in an office job,,or with computers etc, but your life doesn't rely on how you use the equipment supplied. But diving is entering a potentially hostile environment, and making the DM switch over to unfamiliar gear, again just for the ego and attitiude of the DI/LDS, then you're potentially placing the DM and the studetnt he babysitting, in potential danger. If he has issues with the gear he's forced to use, his effectiveness could be adversely effected.