OK... I am starting a new thread because I want to post some pics (at bottom) specifically related to my HVAC sub's ductwork so far (you are welcome 41gasman!) He has rectified a lot, but there is still some stuff I am not pleased with. I base this on reading here, and on Internet research on good flex duct design/install.

I'd like to ask comments on the pics because I am going to get them fixed. The sagging is easily bad, but others may be open to argument. Esp. if I am a consumer -- via my GC who is onboard w/ this -- telling an "HVAC pro" it needs re-work.

Specific concerns:
1) duct passing over duct in subfloor cavities -- he may say that only the outside R6 insulation layer is crushed, not the inner air-bearing layer.
True? ..or comments I can counter with would be appreciated.

2) In many, many places -- and I have no pics here -- instead of using a 3-seam elbow to feed a vertical-boot outlet, they have used mitred floor-boot outlets instead. I have read that this sharp right-angle on the inside turn of the mitred boot causes CFM turbulence at the exit and adds an eqiv. length 40 feet longer than the other way. I want them removed and replaced with 90-corners and vert. boot outlets. Comments?

(See this Home energy Magazine article for that info I used):

As I have posted before, this is an energy efficient ICF home. We are not going to cut corners and the HVAC guy says he will do what he needs to do to make us happy. That is very good! So, I want to be informed and fair when I bring these points up.

As always, your professional comments are appreciated!