Just as finished typing the above I received an email from AS advising they have updated the B-5 user guide to include instructions on how to map midi. Fast work - the updated guide is available online now.

MainStage 3 | Axiom 61 2nd Gen | Pianoteq | B5 | XK3c | EV ZLX 12P
Hoping everyone stays safe and well and sees this through to the other side