Calum,
I recently realized that a bug was causing the TP/GBLk height to not be included in the Z zero set calculation when probing to a mobile TP.
That may well have added to your confusion - the bug is fixed in MSM beta 9.
Dave
Hi Calum,
2) Would it be possible to have the Set Z zero arrow on the WC Offset Touch Off tab made into an action button that would move Z down to the mobile TP on the work? I can achieve this by using the TP as a home switch and setting the offset as the TP thickness but this make the MC Z = WC Z, this is the way I have been using Mach until I found MSM with MTM.
If you click the "Probe Z-" arrow on the probing page it will do just what you want.

The probing page handles "probing events" - i.e. moving until a probe event is seen by mach and the G31 movement is stopped.
Neither mach nor MSM know if the signal came from a probe or a touch plate..... or the push button I have wired to the BoB in my test setup in the office... A trigger is a trigger.
If you have Settings-common "TLO G-BLk is TP" on, you can "probe down to the mobile TP"....