On a job right now that used another piece of Caddy equipment. The piece acted as a craddle that held a four square box but the kicker was that it had legs that brouhgt the box up to eighteen inches OC, and it had side braces for attachment to the vertical studs. I had not seem them yet, it was quite a lot of metal, but it was held in place.
sasco electric does something similar with TI, they use a piece of 14 gauge gal 2"
wide that has a foot the width of the track, and a straight leg off the back of the box to
keep it held forward, resting against the sheetrock on the other side of the wall...
the box comes out spotwelded at the correct height, with a single gang 5/8" ring
on it and a ground pigtail inside.
you blow them down to the floor with a LV gun, and start running MC..... the
bent metal strip holds the box flush with the face of stud, and the bent foot
off the back keeps it from falling back in the wall when sheetrocked.
but an apprentice with a rubbermaid trash can on a hand truck full of them,
tossing them out as soon as the track is blown down, can really scream...
i've seem them have whole floors lassoed together with nothing but
the track shot down, no studs at all.... made up and pigtailed, with the
MC held up by ceiling wires.... no rooms at all yet.... just a forest of outlets...