2013 Ram 3500 Mega 6'4" bed, B&W Companion and Grand Designs

Not sure this will help with your particular situation but our GMC is the short bed with a B&W Companion. I have not run in to any problems and have made some pretty tight turns. Our Excel has the indented corners on the front and I think that is the difference maker. I do, however, watch very, and I mean very, closely when making some hard turns. I think if the Grand Design has the indented cap you should be fine.