How fast is a slo-pitch pitch?

Mark Kelly and I were discussing the idea of a poor-man's Hawk-Eye system - something that could tell whether a pitch falls within the legal 6-to-12-foot arc. The math behind that is outside my purview, so I asked AI. I won't bore you with the whole answer, but one question I asked is, how fast, or slow, can you actually throw a softball and still land it on the strike mat?

Here's the answer: The slowest legal pitch reaches 12 feet and lands on the very front of the plate, crossing at about 27 mph and giving the batter roughly 1.65 seconds to track it.

The fastest stays flat at a 6-foot arc and hits the back of the mat at about 33 mph, leaving the batter 1.1 seconds.

For comparison, a big-league fastball reaches the plate in about 0.4 seconds - so even our hardest pitch gives a hitter nearly three times as long to watch it come in.