Chris Moody over at Floattuber.com (Rob knows about floattuber and doesn't mind me mentioning them) makes a good tubing livewell for $10 I think. Basically it is one of those water noodles that you use in a pool, this is cut to make a ring which is ziptied to the inside top of a mesh laundry bag. There is enough of the bag at the top to drawstring close it. Our tournaments usually end up w/ 100% release, and I personally have never had a fish die. And our tournaments are usually 6hrs minimum. He can give you the dimensions, mine is buried in my car waiting for next week. I don't know how it would work for yaks and skiffs, but worth a try, maybe just use a bigger bag.

Amish Ed