Ducted cooling for 20x40 V-Rail

This is a ducted cooling system. Name sums it up.
It's designed to attach to a 20x40mm V-Rail.
the fans are Sunon 40x40x28mm MagLev (GM1204PQV1-8A)
https://www.amazon.com/gp/product/B00118ZWYY/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

The tubing can be any 1" ID spiral pipe, this is what I used: http://www.ducting.com/ambient-air/dehumidifier-ducts/pvc-flexduct-general-purpose-blue.html
NOTE: On request I have assembled this using standard CPAP hose, it works fine but with less airflow.