I want to add a circuit to a 208 panel, but there are no holes and I really
don't want to go at it with a hole saw.

There is a circuit consisting of one outlet connected to the box by 1/2"
conduit. If multiwire circuits are allowed on 208v, I could put the outlet
on one leg of the multiwire circuit and put my new circuit on the other.
That way I can just put my new MC cable to the bottom of the outlet box,
which does have a hole.

Seems to me that it should be pretty much the same as 240v, except that some
current will always be returning over the neutral; but there is no harm to
that. But maybe I am overlooking something (which, given my knowledge of
208v, is not unlikely)

If I can't use a multiwire circuit, can I simply attach the MC cable to the
bottom of the outlet box and run it up through the conduit to the panel box?
I think 1/2" will take 6 #12 wires.

Thanks.