I understand that the T4 is not direct pin compatible with the audio shield as the I2S pins are in different locations. Looking through the massive Beta thread, there was some discussion about an adaptor board not being possible either because the SAI1/SAI2 pins are both split between the regular pins and back side but I may be interpreting that wrong.

For SAI1... MCLK, BCLK and LRCLK (23, 21, 20) are all on the regular pins but I'm a little confused about the relationships between the IN/OUT pins. For example, can we use pins 8 and 7 (IN1 and OUT1A respectively) to complete the data in and out for the I2S interface?