Plus Man

2006 Larson 268 lxi boat had a 496ho in it boat would run 65mph on speedo . We pulled motor put in a fresh hp 500 efi with cmi headers and a xr outdrive . Boat runs 70 mph on speedo . I am still looking for more speed and wondering if raising my x dimension would this help . I assume this boat being a mass produced boat that originally came with a Bravo III and a choice of small block and big block engines and no tabs that the x dimension would be low. What would be considered a very low x dimension ??