Remdrake, a flat bottom would work fine on the Columbia river, but if you havn't bought one yet, you might look at a vee hull sled, like a Alumaweld super vee. It comes in a 18' and will give you a lot smother ride over the flat bottom. Don't get me wrong a flat bottom fish's and runs small rivers great, but a super vee fish's great in the small river and rides a lot smother in the big ones. Try to get a test ride in both.