i have repaired several places in vinyl boat seats - i got a vinyl repair kit from somewheres online cant remember, basically you cut out the piece of material, test fit it up under the cut/hole for a backer to stick the torn/ripped/cut piece to as needed.
biggest thing i learned from it is wear rubber gloves, use popsickle sticks to work things around with, get out lumps, do it when its REALLY WARM, or if working inside put a heat lamp on the area to get things REALLY pliable.
Heavy objects like weights/bricks are great for adding pressure to an area to hold a crack together while product dries/cures
the stuff i used was gooey and u brushed it on to set up and it didnt take long took several coats
not like new but waterproof and stopped any further tearing - my wife gave the thumbs up so thats all that mattered!!!