I'm installing recessed lighting fixtures in the ceiling of my second
floor (below the third floor--hence no insulation) in an old
Philadelphia house. The problem I've run into is that the hanger bars
for the fixtures collapse to 14 inches, but the beams are only 12
inches apart. This is essentially "new construction" because I've
removed all of the old plaster ceiling and will be replacing it with
sheet rock. I can see a few possible solutions. One is that I create
new beams by installing 2x4s between the beams at 14-16 inches apart
and then hanging the fixtures as I would if I were working with modern
beams on 16 inch centers. Another option would be to modify the
hanger bars with a hacksaw to make them collapse to 12 inches. Or, I
could look out for some specialty fixtures that would fit. Finally, I
could take the Home Depot attendant's advice and "just let 'em sit on
top of the sheetrock" (which I'm extremely disinclined to do for a
number of reasons). I would appreciate any guidance. Thanks,

Andrew