Hi, Alan. For what it's worth, I mounted a standard CB antenna (you know, with the big magnetic base) to the top center of a GTS rear glass using alcohol to clean the glass, then a LOT of racer tape (red is faster) in 1 ft. lengths going horizontally, then vertically...with the wire providing additional support as it was pulled tight and "fixed" inside...used Cobra 4 watt...and all the trucks thought that it sounded fine.
This worked well on a 600 mile trip, with "wind tunnel" testing to 140 mph ("closed course, professional driver, etc. "). I did check it for retaping but did NOT have too.
Use at YOUR OWN risk...p.s....let me know if you come to your favorite (if not jinxed !!!) state and I'll try to find a rear glass just in case.