how about welding a sheet of aluminum over the ribs and to the edges. that would make a bit of an angle from the most outside ribs to the side edges of the boat. thoughts?

weld a peice of square tubing on each edge of the bottom and them weld the slick bottom over the runner and all, you would have a seal welded double bottom.

Out of curiosity, why are smooth bottom boats sometimes preferred over ribbed boats?

Less drag, you slide over mud and grass much easier.
In stumps the boat will slide off instead of hanging up.

Also, if you have to turn it around in mud or grass when hunting you will definetly notice a difference.