At a small jet rally this past summer I pointed the radar gun at a couple of different airplanes.
Kingcat with Titan SE on the level was about 215mph. After a moderate downhill run about 255mph.
Bobcat with P120 was about 265 in a shallow dive.
Altitude was just short of 3000 feet... Temp about 75 degrees.
Obviously these jets are capable of speeds well in excess of the legal limit and I'm sure many already know this.
Keep this hobby safe so we can all continue to enjoy it.