What are the guidelines for QVM and CMC?
Basically, Ford supports converting Town Cars up to 120″ (10 ft. added to original chassis), Excursions and Navigators, up to 140″. General Motors supports 130″ conversions of the DeVille. The manufacturers have determined, through extensive (and expensive) testing, including crash testing, that these platforms retain the structural integrity for safe highway operation. A conversion in excess of these lengths is not authorized by either manufacturer and voids the warranty. Of course, there is much more to it than this and if more information is necessary, please contact the manufacturer.
