I don't think Caddy makes a T-Bar hanger for 4x4 tiles. (Or do they?)
These fixtures must be independently supported, but the support fastened to the grid.
We use support wires fastened to the structure above, and EMT screwed to the housing/box and tie wired to the grid to achieve this on a 4x4. (But then again I'm in SoCA=earthquake)
You might want to check the Caddy IDS hanger if this is a surface mounted fixture.
Don't depend on the tile for any support at all.
It wouldn't hurt to call your AHJ and have them tell you what they want
[This message has been edited by electure (edited 04-10-2002).]