You "shoe-horned" a 7.5T unit into the corner of a storage area with large duct using the plenum/ mixing box theory of duct sizing and did it in a neat, workman like manner that is a good reflection on the pride/care you take in your work.
For those they think they could have done better with the limitations that were handed this gentleman ( look at the doorway, and electrical fixture location etc
I wonder how you would have been able to improve on his work product
I suspect that the relatively velocity in the large, short duct run you describe could have used more than 0.1 of static.
PS, I also applaud your neat use of board. For those who would have used sheet metal (bare or wrapped) I guess you would have told the customer they need to live with the noise.