Ok, its a basement. We had our ac replaced a few years back and had them run a few ducts. We do not expect it to make a huge differnece...we knew that going in...the one duct is right above a seating area though and in the winter is seams to make some difference.

So I put up my grid for my suspended ceiling and got all my cans where I wnated them and got everything wired up. I was just about to start putting tiles in when I realized I forgot about the duct! Of course its between two joists but a grid pretty much runs parrelell to the joists almost splitting it. Bottom line, I have a 6" round steel duct with about 2' of plastic flex coming off it sandwhiched in an area about 8" wide. I have no idea what to do about a boot grill and how to attach it.

The one thing mentioned was a 6" circle diffuser attached to the flex duct, resting on the ceiling tile with the grill attached the ceiling tile. Simple enough BUT...Is this size grill big enough? I see 6 x 10 boots, 6 x 12 boots etc etc...those are all bigger than a 6" round diffuser/grill. Is this just cosmetic or does it make a difference what size the boot / grill is?