Using aces at an event relative to expected number of aces for the field playing (ie how many more aces were achieved than you would expect given the players ) he works out relative surface speeds of different events. Stuttgart grass, Wimbledon and Queens and Halle all feature highly.
He also analysed the sensitivity of court surface speed to a particular player and those who we can expect to therefore seeing doing better on faster surfaces, focussing on the inform Ugo Humbert who did well indoors and then came unstuck on the slower indoor courts in Rotterdam versus Ruusuvuori, who seems to regularly beat Humbert on what turn out to be slow courts.