Interesting discussion, at least to me who has had perhaps more limited access to different controller types than you guys!

Absolutely right, Dean - I got my G90 and G53 in a twist. Stupid of me - I've used enough of both in things like tool-height setting macros to be aware of the difference. Your detailed description of why absolute/incremental around the G28 is needed is a subtle point that isn't really that obvious when you read the manuals. Not until you've driven the tool through the bed and then had to figure out why...

I've only used G28 in the context of Mach3/CSMIO and MyCNC/ET6, and it works the same way in both - "go to predefined ref posn", and the user can specify the ref posn in parameters somewhere. Sounds like this is rather different to the Fanuc interpretation. Another case of "both are right but both are different" - you just need to understand what's happening. Now I know about the Fanuc view of G28, the SZGH manual makes a lot more sense. I would guess that they have added the "G281" etc format so that instead of
G90 G28 Z0
G91
you could just use G283 ("move to ref posn along Z axis")
Not that much of a saving, really

I understand the point about the Fanuc G30 taking a position parameter for the destination position although moving via an intermediate point. What I read in the SZGH manual, though, sounds as if the position parameter concept doesn't exist and they use the work coordinate zero as the final destination. Frankly, I'm going to end up experimenting once the machine is up and running but even if we end up redefining machine zero somewhere other than the home switch position because that's more useful for manual tool-change, that's not a big deal. I've left the default action in F360 to move to the toolchange position at the end of a toolpath in place although Muzzer's idea of making that a tick box option in the PP is interesting. On the odd occasion when I've wanted to move the tool out of the way at the end of a run, I've edited the gcode manually.