A light weight tandem shouldn't be much heavier than an average solo canoe.  You should plan to sit more in the center of the length of the canoe, so some kind of alternate seat??
Maybe a deeper keel or skeg would help with straight tracking on distant paddles.
Anyway, I am dedicated kayak paddler so really don't know much about solo canoes.  MY Poke boat only weighs 28 pounds and I have gotten three weeks of gear and food stowed into it.  Kayaks are hard to stow all your gear in, bulkheads and rudder cables etc. can get in the way.  If you have a kayak without too much under the decks it makes getting the gear into it much easier.