Thanks, Mecanix - that's a very kind offer.

But, to my mind, the post should be nothing more than a translator from CL to machine specific code. Putting smarts in there where it can't be tested easily sounds like a trap for future dharmic who has forgotten whatever cleverness I might do today.

I'll keep playing with a combination of adaptive clearing and the Flow tool. The big trick here is in trying to minimise torque on my 4th which is just a gutless little stepper on a 3:1 or similar belt.