Wow guys, thanks for the support!
Gofer, have now fixed the zero-size bug (replaced with 1 - I tested a variety of different heights, but 1 is the least intrusive visually, and also still shows selection clearly), thank you, wasn't aware.
Also fixed a couple of minor skin bugs and edited it slightly - ever so slightly brighter in the edit window, plus a few other things like grid z-layering.
I would be highly delighted if this became a sticky!