http://nativewatercraft.net/ultimate12.html

What they call "Tunnel Hull" is a catamaran type of hull and
according to the hype you're supposed to be able to stand up
and fish out of this thing.

Ken Fortenberry

Seems to me like it would have high initial stability, but low
ultimate stability. Which means, it feels stable, like it won't go
over, but when you hit that tipping point, you are going over for
sure.

Hull designs are always a trade off in that respect, it really depends
on what you want.

The really cool model they have over there is the Compass / Wee Lassie
copy designed by Rushton, now that is a beauty!

For a real stand up Kayak check this out...
http://www.freedomhawkkayaks.com/Freedom_14.htm

-Ethan