Rod: SuperDuct RC questions

I'm looking at the option of utilizing the SuperDuct RC product for my basement studio portion of my house. This is for live rooms only. The control room is separated and on another floor. The HVAC currently supplies the basement, so I'm just altering where and how it's directed. The current air supply is 6" round galvanized tubes connected to a huge rectangular plenum spanning the entire length of the basement. I'm going to try to line the giant plenum as much as I can (possibly just the bottom and one side on both supply/return) using 1" blanket style lining. I'm looking at taking the 6" round feeds to the basement and converting to SuperDuct RC (6"x12" most likely) for the last 10-15' of the run to the rooms. Questions: 1- Are these 'Field Fabrication Kits' the way to go? (as opposed to having each piece fabricated) 2- Would you still recommend silencing plenums near the vent openings? (It appears that these would be easy to make out of this product) 3- Would I need to isolate the SuperDuct from the metal duct mechanically? (short length of flexible 6" pipe between the two) 4- The basement already has 2 feeds and 2 returns. I'll be adding a third. Should this be fine to compensate for the reduced airflow from lining the main rectangular plenum? (losing 1" on 2 walls, but increasing flow by 1x6" send/return) footnotes: can't easily get to the 90 degree elbows on top of main plenum all ducts run between 2x10 joists (~14" space) private use home studio have your book & find it indispensable enjoy fine wines, acquiring tools, loud music of all genre's

5- Is 1" thick SuperDuct RC appropriate for this use?

Bump, and also if anyone else has opinions or experience with tapping into a metal ductwork HVAC system it would be greatly appreciated. Original plan was... Run long lines from the main plenum (15' plus). Slow the air down with a baffle near the plenum. De-couple it/change directions a bit with a length of 'flexible' duct Fit that to a silencer plenum. Another flex duct to the wall register. Wondering how much isolation is to be expected from these rooms to the house upstairs, and if the using the rectangular SuperDuct is a more elegant solution (easier/more efficient/better isolation).