The outer rail should do the trick , all you need is something to maintain the shape and keep the wood from flexing outward and what is better then a rail on the outside holding the sides in.
If you try to pick up a pirogue without the outside rail on it the sides will flex out and usually end up cracking one of the boats ribs , if not breaking them. That is one reason why I always warn a person to have the outside rail on before trying to move the boat by themselves , or doing it carefully with a friend.
The outside railing and the ribs are what holds the boat together so nothing else is necessary. This way you have a wide open boat.
The inside rail is more for looks and I like them for traditions sake plus they are great as tie off spots for things in the boat , if a person is prone to tying things off in there boat. I do hang the container for my Water Bottle from the inside railing , puts it right there for a quick sip when paddling.
Chuck.[/QUOTE
I plan on getting to my someday a UJ around 16ft, instead of the sides parallel I am thinking of adding more shear 12" at bow, 10" midships and 11" stearn. I will be using 16' lattis strips for gunwales and inwales, how much trouble should I have with bending it to match the sherline. I can't afford clamps so I am thinking of each 3 - 4" schedule 40 pvc tube split for clamps, easy question for bunch of "Pirough Phds"