One of the more irritating tasks while turning is measuring the rate of progress. You can remove metal, more difficult to add it back on!
I read on Start Model Engineering about using a digital tire depth gauge for this. For $8 (free shipping) one arrived in the post after a while.
A bit of machining and voila, a DRO. Still have to decide how to best mount it although I at the same time replaced the 8mm rods with longer ones. This should provide room for the DRO as well as allow me to mount a stop.