12" long direct in line would take more room than I am looking at and more as the duct is supposed to go on the inside and the filter opening is also the female bit so would need at least 4-6’ more for that midpiece.
It will not be as nice as originally designed but it will set up a centrifugal spiral that will throw larger pieces out from the center. It will also reach 4" beyond the face of the filter instead of 12+.