I've done a number of boat "canvas" projects for myself and others. Ive used 303 Fabric Guard a lot and like / recommend it to others. It is the recommended treatment by the maker of Sunbrella, an acrylic fabric. I will never understand why anyone would spend the $ for a quality boat canvas project and not follow the mfg recommendations for care.
From the 303 mfg site...
"303[emoji2400] Fabric Guard[emoji769] is designed to be safe for use on all natural and synthetic textiles and blends. It should be safe for solution dyed acrylic, polyester, nylon, cotton, wool, silk, and fine leathers like suede.
Do not use 303[emoji2400] Fabric Guard[emoji769] on vinyl, clear vinyl, plastics, rubber, fiberglass, or imitation suede. Consider*303[emoji2400] Aerospace Protectant[emoji769]*instead to protect and beautify these materials."
I have talked to a 303 tech rep re best practices as I was not getting the results I expected and he provided the following recommendations...
Thotoughly clean & dry before treatment
Apply to suspended material (not layer out on a surface like picnic table, etc)
Spray apply, multi coats in a criss-cross pattern to get complete / uniform coverage.
Avoid soaking the fabric, multi light coats are better
Best to Apply in full sun on a HOT day... hotter the better (I was always doing my canvas in spring when it was cool and doing it my garage out of the sun)
Let the 303 set in the sun to warm... do not bring it up from basemen ot out of a cool storage location and apply
Using the above I had noticably better results / performance.
My guide is if it's a woven fabric I'd use 303 Fabric Guard per above.
If interested in whether it is synthetic or natural yarn used try heating / lighter flame or soldering iron on an inconspicuous piece of excess hem material edge. If synthetic it will melt, if natural it will char but not melt. With 303 FG it doesn't really matter as it works for both.
Lastly... Sunbrella (& many others) do not recommend using silicone products as they leave a oily surface that attracts and holds dirt and is very difficult to remove. Dirt is the enemy of fabrics and will cause unnecessary wear and premature failure.