Full disclosure: I haven't used it myself, and to be totally honest, I hadn't considered this application, either, until you posted your question!
I ran across it a month or so back looking for a spray-on product that would tint the inside of two Lexan headlight covers I was going to purchase for an old sports car taking up space in my garage. Considered this product because one of the commenters on Amazon said that he had sprayed it on glass, then used an X-Acto knife to cut and peel away what he didn't want.
Sounded good to me, but when I went back to buy the covers, they were gone! Still looking.
Anyway, let me know how it works out... the canvas on our '97 Viking is starting to show its age, too.
Michael, Suzy & Arnie Asada (Chihuahua)
'97 Viking Legend 2480
'19 RAM 1500 Laramie 5.7L Hemi