Roscoe is a teaching pro at my club. i asked him yesterday what he thought his serve speed would be using todays equipment. his answer surprised me. for the record he was clocked at 153 mph. he did noy think there would be a difference and this was his reasons why. he stated that after wood rackets the racquet he used had similar "silouette" to the modern ones . ie aerodynamically similar. the radar gun measures the speed of the ball off the raqcquet (at contact). so if you could generate the racquet speed even with a heavier racquet the speeds would be the same."its all racquet head speed". also he believes the white ball used then had a different felt cover and the rubber core was livelier than the balls today. so a slower modern ball would have an impact lastly he told me that Phillipousus noted for his big serve was measured using older racquets and his modern raquet and the difference in top speed on the serves was ONE mile per hour!!!