The source of the fabric is a non-issue other than price. Unfortunately, it seems the inexpensive uncertificated 1.8 and 2.7 fabrics we used to get from Aircraft Spruce are no longer available. This leaves you with one of the uncertificated light fabrics from a major vendor such as Polyfiber:

https://www.aircraftspruce.com/pages...ncertified.php

You can do tests if you wish but this is a proven method with nearly 30 years of field history.