We used some eternabond tape and it held for 3yrs before the rest of the canvas gave out (the tear never got any bigger). Just wrapped it around top and bottom.
When it did reach the point of no return. I think it was $160 for new canvas for a large slideout and took about a 1/2hr to replace. It was an easy job.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV