Reel-Break,
I was tripped up on this one some years back. It was with a recessed fixture, rated for thru-branch wiring, but it had a small opening. There is a problem with the UL listing of the fixture. UL list recessed fixtures with an opening smaller than 6" to have its junction box very close to the opening to be rated for thru branch wiring. I forget the equation, but it has to do with adding the distance horizontally and vertically that the bos is located from the opening and comparing this amount to the diameter of the opening. If you need it, I'll look it up
