DO YOU RIP through floors and double walls 2 and 3 stories?

A few have mentioned no high returns below Cincinnati lines out of ohio...
Where do you fee is a good zone to lower Returns.
Floor returns have proved the RADIANT folks correct with stratified HVAC.
I have found the high returns and diffusers - made to less-difuse from a ceiling supply, eliminate stratification and stabilize the air to about 1-deg differences.
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Are High and more central returns very good in your projects?

From Dayton to OH Erie PA and Detroit MI putting in high RETURN-AIRS (Ra) are with a lot of cutting along sides of stairwells, up along making double walls anywhere can allow chase construction.



Building through framing systems into attics with sealed double walled duct board has been used whereas the inner box is foil inward and the outer 2nd layer of duct board is foil outward and large enough for collection of all other local returns , the other rooms not always using stud wall return grills but ceiling mounted returns, if acceptable.

Unconditioned spaces, just as if for Air-Solar for many years, are not a problem in sealing properly nor insulating well for low losses.
All flex insulation coverings of r-6 have more 2" foil duct blanket or something better from NWOHP.com foam and linings and some recycled.
All silicone sealed screwed, glued whatever--- very tight. Burying in cellulose another 6" over top seems to not show a 1-degree loss through runs returning air across vented attics , below zero weather.

But several folks still feel not a 'best'.

Comments?
The homes are dryer running more A/c a bit, but the heating bills are much much lower and comfort seems super with 'cleaning the air by filters  24-7  with the constant fan: 12% recirc to some customers want about 20% on always of total high blower air speed. No registers disturb walls either.

High Cooling mode acceptable R/a seems well enough when highest efficiency heat recovery occurs with 100% Priority HW -: the extra A/C may be more helpful in savings overall.