As topic, request adding AnalogWrite() 'pins' to the Pads available on the bottom of the Teensy3 - they have the same PWM capability as the existing Analog Pins on the headers (FTM1).
hardware\teensy\cores\teensy3\pins_teensy.c
void analogWrite(uint8_t pin, int val)
OK I looked into it a bit more and need to shoot this idea down myself so not to waste Paul's time on it.
Summary :- Pin 24/33 on the SMD pads on the underside whilst PWM/FlexTimer pins, can't be used because the FlexTimers are currently used to drive Pin 9/23.
From (1), the underbelly of the Teensy3 has SMD pads for 'pins' 24 through 33.
Teensy3 'pins' 24 & 33 are in the same group of FlexTimer capable pins used by the current AnalogWrite() for PWM.