DRO for mini-mill

Hello all, this is my first post to this group. I have a mini-mill
(similar to Grizly etc but with 10tpi leadscrews on all three axis)
and want to get DRO for it. I'm going nuts using just the little
scales on the handcranks. I see there are inexpensive scales to use
for this purpose that can be either used stand alone or with a DRO
box. What I haven't figured out is what part of the scale gets
attached to what part of the mill for each axis. The vertical axis is
easy, its the X and Y I haven't quite got figured out yet. I'd
appreciate any hints how to get these hooked up.

Then there is the issue of the DRO box. I saw a mention here of DRO2
which seems good for the task except its only 2 axis, I want three (I
could do it with 2 DRO2s but thats getting a little expensive)

I'm an electronics engineer, doing any PIC based boxes and stuff is
easy if anybody has any plans for this sort of thing.

Home machining is a resent endeavour, primarily to support one of my
other hobbies, telescope making.

I eventually want to get this converted to full CNC use, but for now
I'll settle for getting DRO working.

Thanks,

John S.