Walls and Ceilings - Drop Ceiling in basement

My father-in-law and I are installing a drop ceiling in the basement of his house. The ceiling is roughly 750 square feet. The challenge we face is that the duct work hangs to 6'10" and is about 14" off one of the walls. I would just box the duct work, but along this same wall is the stairwell and a door leading to the storage part of the basement. With this in mind we decided to angle the tiles at roughly a 30 degree angle around the duct work. As the tiles return on that 30 degree angle back to the wall, we are experiencing a potential problem with the tiles not sitting correctly in the grid work. One person told my father-in-law to angle the grid work along the wall to let the tiles lay better. Is this the best way to cure the possible problem? what about the grid around the duct work? Will we have a problem with the tiles there as well? Any help would be great. Thanks.

Your grid has to be on the same plane as the tiles will lay, so I'd say yes the grid needs to be angled. Good luck. ;)