These are my fix for the rear floor vents for 2014 to 2018 Chevrolet Silverado and GMC Sierra. These may work for the Tahoe's, Yukon's, Suburban's, etc… vehicles with the same ducts.
The major problem was the duct collapsing and slipping under the carpet. I tried 737mechanic's version but they didn't fix both issues for me. His design did inspire mine but I started fresh to fix both issues.
The author marked this model as their own original creation.