Pix32 v6 is compatible with Pix32 v5 Baseboard and vice versa.
There are some port that will be non-functional when using a Pix32 v6 FC on a Pix32 v5 Baseboard. Please refer to Pix32 v6 Baseboard Ports & Pix32 v6 Mini-Base Portsfor more Detail
Pix32 v5 Baseboard & Pix32 v5 Mini Baseboard Dimension