All - I am looking for a 2x20 pin header that allows shields to be assembled from both direction on the RPi zw. Meaning, we can mount headers on both sides of the RPi board. Any help is appreciated.
If they are real HATs (follow the official HAT spec), then they will conflict (except for the PoE HAT, currently, as that uses a different i2c address).
This ^ as Imperf3kt said, you can't just plug a HAT in upside down. That will not end well.