Problem is, camera speed is not always the same, and can depend on battery condition, court temps, and some other factors I don't know.
Just like computer speeds, they are NOT the same day to day.
TennisCJC, your examples correlate with mine. 100mph at 50% is plenty good enough for any kind of match play, because that 100 puts the reciever where the server wants him, so he can hit a spin serve in as a first serve, to effectively force a weak return.
For me, playing at only 4.0 levels, a 100 mph first serve at 40% works just fine, especially since my second serve is around 95%, hit as hard as I can swing, and much more spin and faster than any second serve of ANY 4.0 who doesn't double fault, and it's lefty with excellent placement.
Plus, the ability to hit 100 on the fast first serves allow a more consistent flat first serve that goes in more often at 93 mph, which is fast enough for an ace once the returner starts to cheat to one side or the other.
It's not always the pure MPH that get's the ace, it's the positioning of the returner opening up a huge court to hit into, where a slower serve can be a clean ace.