Hi Mike, thanks for the reply. Sorry, wasn't clear on origional post, the option is on the xpro flash controller however once connected to either the 5dmk3 or the 7dmk2 the flash will only fire first curtain. checking the in camera menu for flash control it does not give the option for rear curtain, only hss & first curtain.
when using my yongnuo flash/controller setup on both cameras i can set it first/rear/hss both on the controller & via the in camera menu.
Assuming from the certanty of your reply you have had experience with using the canon/godox setup? From that I'm wondering if either I'm missing something completely obvious or the potential of a faulty unit.