This is a blend of Pinky's Papst EBM backplate (heat insert variant) with the 4028 gaping maw fan duct by Idrake88 ( https://www.thingiverse.com/thing:5330852 ) along with some adaptions.
This allows you to use the Papst EBM fan with tensioners and MFBS “Gaping Maw” fan ducts which are much wider and allow more airflow.
Please note that only M3x4,6x4 heat inserts will fit.
Thanks to Hopfenschorsch for being the first one to try it.
05/05/2022
Update to 3.2 - Fan duct perimeter width and the perimeter width of the fan “lip” has been increased for more stability. Also I unified the heat insert size.
The author remixed this model.