Opening in drywall was cut too large, now cannot figure out how to install a ceiling register.

tl;dr Is there a way to step-up the size of the opening of a duct (10x6 to 12x8) where it comes through the ceiling?

In the kitchen there was a dropped ceiling. When we purchased home we decided to bring the ceiling back up to the height of rest of house. The drywall was put up before the duct was cut up to the ceiling height. This created the problem that the hole is too large around the duct opening. It should have been cut to cover the "lip" of the duct coming down.

Please see these pictures.

If there was a way to increase the size of the duct opening - from 10"x6" to 12"x8" - I think that would solve the problem. But I don't know how to go about doing this.

Is there a way step-up the opening size?

submitted by /u/donuts_donkin
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