Ok, I can confirm that the motor layout is different for tricopters on PX4. I now have the motors & tail servo set up right.
After looking at the PX4 motor map, you can see that motor 1 is always in the upper right quadrant. That makes motor 1 an easy guess. Going counter clockwise is motor 2 & 3, with the tail rotor as 3. Tail servo at #4. Makes more sense than APM.
Now I just have to figure out why the servo yaws to starboard on power up & I keeps trying to push past the servo's limit until I arm with the button.