In article ,
"Daniel L. Belton" wrote:

The best option would be to place the 2x4's between the joists and mount
the fixtures to them. I wouldn't let the fixtures just sit on top of
the sheetrock like the HD guy said...

Uh, but it seems to me that putting 2x4 between the joists doesn't
remedy the fact that this guy is trying to shoehorn 16" wide hangars
into a 12" wide space.

Unless maybe you're talking about screwing 2x4s along the length of the
joists and attaching the hangars length-wise. But that would be kinda
silly, seeing as how the cans fit pretty nicely that way without 2x4s.
But if someone was intent on hanging something inside those joists and
mounting the cans sideways, you'd get by far less expensively by hanging
1-bys -- but then, the cans wouldn't fit.

AJS