I am building two mice for our small family of four. I'm going to stack them like paper cups to put them on top of the car so we can drive to the local estuaries and rivers. This means the outer mouse can have no internal bracing.
I beefed up the gunnle with an two 3/4" x 5/8" stringers separated by 3/4" spacers. When I took out the cross braces, the gunnles only deflected inward 1/8" of an inch. The inner mouse will be made about 1/2" thinner than normal. Inner mouse still hasn't been built.
Below is a picutre of launch day, paddling upstream fast moving creek in May 2004. I did some whitewater mousing, surfing behind a small standing wave in the middle of the creek. Fun! That's a greenland paddle I made from a 2x4. Not the best for shallow whitewater mousing, but sufficient. Plans can be found at: Qaannat Kattuffiat, the Greenland Kayaking Association