Interesting idea but that's a lot of boat to hang from the davits. I saw an outrigger kit at the local outdoors store - haven't seen them in use though.
Each sportspal canoe weighs 72 lbs or less (heaviest model is 72 lbs, lightest is 48 lbs), plus whatever poles you used to connect. So less than 180 lbs total (assuming 40+ lbs for the framing). Considering it can be broken down to form two separate vessels if needed, I like the flexibility.
If you want to get fancy you can even add a deck
between the canoes, for a little more weight of course.