If I understand your problem, some of the ribs protrude from either the top or bottom of the leading and trailing edges? Or, the ribs do not even reach the top or bottom of the leading or trailing edge, therefore leaving a gap (hole?) that then has to be filled.
And, you say all parts are true an straight? The only thing I can come up with right now is that maybe the rib profiles on the plans are not drawn perfectly symmetrical. That might account for not being able to get the ends of the ribs to match the leading and trailing edges.