I never really finished this How-To, so I'll resume now.
The
Loctite Vinyl Fabric & Plastic Repair Flexible Adhesive is critical, and it is what actually makes the repair. The Black Permatex Silicone is mostly cosmetic, it doesn't add a lot of strength to the repair.
Ideally, the Loctite actually dissolves the surface of the existing vinyl seat and the surface of the backing material, resulting in a very strong "welded" repair.
I tested several vinyl and fabric repairs and adhesives, as well as several different backing materials.
I've used
Plasti Dip VLP Vinyl Repair 61Z09. It works just as well as the Loctite, probably because it's exactly the same. But 3X the cost, and harder to find.
I've never used
GEAR AID Aquaseal FD Flexible Repair Adhesive, but it looks promising. Again, probably the same stuff as the Loctite at 3X the cost and harder to find.
There are several other products that have "vinyl cement" or "vinyl adhesive" on their labels but the Loctite works and is cheap and I would keep away from anything else. I've tried PVC cement -- seems like a logical choice since it dissolves PVC, but no, it doesn't really work on vinyl.
I've tried various fabric adhesives from fabric and crafts stores -- they are a definite "no." E6000 -- no. Flex-Seal -- no. Flex-Glue -- no. Gorilla Fabric Glue -- no.
Onward to the backing material.
The Walmart Flannel-Backed Vinyl that I listed back in post # 6 won out over everything else that I tested. It's vinyl -- so the Loctite will melt its surface.
If you go all the way back to the first few pics that I posted in this thread, I was using a blue backing material. That was rip-stop nylon, readily and cheaply available from any fabric store. It works okay, and is slick, and thus very easy to position under the torn seat vinyl. The Loctite sticks to it well, but doesn't really dissolve it.