I was wondering about compatibility between Teensy 3.6 and 4.1. I can see from the pinouts charts that there is a significant difference, but how big is the difference really? I am currently using pin A4 and A5 for I2C. A7 for reset, A8 for TDM and 9 for BITCLK. I would also take advantage of the fact that Teensy 4.1 has 2 TDM, where would it make sense to place the TDM pins?

Thanks for the help!