I was thinking you asked about the standard amb kress, didn't see it was the one with quickchange, but glad you found it!! Good luck with the installation :-)
Hello Andy, the openbuilds/ooznest standard router mount needs a reducer to 43mm. Ooznest sells 3D printed router mount adapters.
You can also buy an aluminium router mount 43mm from sorotec.de (without backplate to attach to the Z cbeam) or from makersupplies.dk which has already a backplate to bolt it to the Z cbeam. They're both the same mounts only the German one has no backplate. If your choose the one from sorotec, I can send you the design of the backplate I made myself out of 8mm aluminium.
Beickybeer / Christophe