Download our flat bottom boat design for the extreme flats 20, a light weight, quiet hull with low freeboard. buy flats boat plans and more at bateau.com!. Power boats between 17 and 20′ loa. some with cabin.. Osprey 18 flats skiff. the osprey 18 flats skiff was originally designed for a client (who stiffed me on half his bill!) in louisiana back in 2008..