Just put pins on a new T4.1, loaded and compiled Blink, and the Stats Window in the IDE shows over 8Mb free! That seems unlikely, so I did something wrong. Ideas?
No, that is correct.
Teensy 4.1 free Flash is 7936kBytes which is 7936*1024 = 8.126.464 Bytes.
Note the multiplicator 1024.
(Not 1000, as Harddrive suppliers use it)