Like I posted earlier I got mine on the 16th. The air duct was about 3/4 inch to long, I cut 3/8 inch off of each end with a pair of scissors. Then I used black shoe polish to cover the blue silicone on the edges. It looks very good I tried to crush it with my hands. If you noticed the middle of the duct bulges out, I could not pinch the middle in as far as the ends. I don't think any additional interior support will be needed.
Thanks Jim
Here is a picture
