As a long time redwood/cedar strip and fiberglass canoe builder I would recommend that you keep the redwood for strip canoe building. The redwood is more brittle and unforgiving when bent, than cedar. The strength to weight ratio is about the same, but I think that you would lose a lot of wood to breakage when building a wood canvas canoe with redwood. It would probably break or split just as you are putting in the last clinch nail to that rib or plank!
On another note, redwood will bond well with polyester resin fiberglass, while cedar will not. Both seem to be about the same with epoxy resins. I still have one of my first canoes I made in 1971 with redwood and polyester resin. It has been on over 12 extended Boundary Waters canoe trips plus many other trips. The redwood has darkened (or taken on a "patina") over the years, but it is still very beautiful while looking like a dark red mahogany multi-colored canoe, and the fiberglass has not separated from the wood at all. It is still one of my favorite canoes, and the plans were from the Minnesota Canoe Association.
I have not used redwood in any of my wood and canvas canoe building projects, but would like to hear how your project works out.