Reg,
I'd guestimate about 3ft. between the walls and the walls to be about 12" high. The weight capacity is 1250lbs and is said to handle up to class 3 whitewater. The boat is very stable and you can certainly stand and flyfish from it. It can handle up to a 4 hp. motor. As I said, I only used an electric on mine and the reason I didn't use it more was that I got a 16ft. tri-hull that sorta became my son and I's project and we spent most of our boating time on it. I'm a stream fisherman so this was all kind of new to me. There are certainly some cheap inflatables out there that aren't worth a crap but I think sea eagle makes a quality product. If you look at their website you'll see inflatables that handle 40 horse motors and do some pretty impressive jumps over waves. Just MHO and hope it helps. Bruce