I can't help you but have an observation.
If the tent is truly canvas, the design is out dated 20 years or more. It's not a reflection on you, a lot of tents for the mass market still use canvas, but there are much better materials now. Lower volume but high quality tent makers use them, Pahaque, (for one that has r-pod related stuff) is an example. I personally would not touch a tent made of canvas with a 20 foot pole. (Except for specialty use - like my reproduction revolutionary war era lean-to.)
My only suggestion is to go to an awning maker if one is in your area - they are getting scarce, and see what they say.
Good luck
