For aircraft built under FAR 23 and the materials used for any
covering, FAR 23.853 is very clear. You have to test it to FAR 23
Appendix F. Commercial and automotive materials may have been tested,
but not to meet that FAR. There is no distinction between natural or
man-made material. If it goes in a Type Certificated FAR 23 aircraft
it gets tested. CAR 4b certified aircraft probably have to meet a
lower standard, but why take a chance? I don't work in the small
aircraft world, but I'm sure there are many shops out there that can
do reputable work with proper materials and sign off what they do at a
fair price.

If I were to accomplish an Annual Inspection on an aircraft that has
been re-covered, I would review the burn tests and log entries. No
required burn test documents and log entries and it is unairworthy.
So it looks like you have some options. Try it on the cheap and risk
your life and the probability of having to re-do it properly at
annual time (on a Part 23 aircraft) or doing it right the first time.
The other option is homebuilding. You are free to put in materials
that may kill you and do the work yourself, but at least you die
legally.