I was just reading the info on Gluvit. All the post on here refer to it as being used on the inside to seal against leaks and Steelflex on the outside of the boat for protection. Why can't Gluvit be used on the outside for sealing and coated over with Steelflex for protection? Seems like the Gluvit would provide a little give for the Steelflex with boat flex. Has anyone tried this? Does this seem like a problem?