"What we want the knife to do.....& where." Having lived in, hunted the boundaries of, hiked, fished, camped, rode horses through Federal Park lands since before I could legally drive I know you can't really Build a knife to legally use & do anything within the laws within the parks. Instead common sense & safe use are the best guidelines. Unless you just build a 10-3 (a GREAT knife) & done with it. And if you try, the laws will change tomorrow.
Build the knife you'd use in the parks....or the one you want to keep on a shelf, without worry re: state & federal laws. Too many irritating things otherwise to just argue over.
Or heck, if an incredibly useful & wonderful addition of top sharpened blade is too much, #28 can't be beat. What a blade!