Ron, mate,
Matts assymetriccal tourer, is a great boat - even without the tumblehome.
The tumblehome panel will stiffen and strengthen the sides a lot. I bloody love my tourer but I think this new version will be much better.
The more I look at those concept drawings of the new tourer, the more inclined I am to relent to some serious presure to sell the one I have now and build that one.
I am sure that with your skills and experience designing and building hovercraft, that you could design and build a very good pirogue of your own - but why bother? The plans are allready there. They are as cheap as dirt and the boat works.
Come on over to the dark side of Matts lovely pirogues mate. You will never regret it.
Oh yeah, Matt, P5 is your call and I respect that but it really is a fine boat and is well worth keeping on hand. (Perhaps, even as another freebee if you must

)
Bloody freebees All Matts boats are too bloody good to just give away