downclock the freq from 700 to 500 and set the fans to 35%  or 40% if you put it in the tube

then buy this wait for link

https://www.homedepot.com/p/12-in-x-25-ft-Insulated-Flexible-Duct-R6-Silver-Jacket-F6IFD12X300/100182573

https://www.homedepot.com/catalog/productImages/400/01/01320a0c-e964-4554-a0f3-984756960ffc_400.jpg

here is  a mock up