How can I prevent negative Bonjean curves ?
A decreasing Z-order (i.e. deck to keel) for the points of a section results in the Bonjean curve for the section being negative. The solution is to fix this error via the Reverse Point Order option in the Edit Element dialog, Fix Errors menu. If Bonjean curves are negative across a range of sections, the process may be done just once: see HST FAQ 3.11.
