I used some T-track from Woodcraft: http://www.shapeoko.com/forum/viewtopic.php?f=37&t=8332&p=65068#p65068
For spacing, I used various widths of PVC "lumber" which I use as a spoilboard --- this is always a bit tricky --- you want the smallest spacing to be equal to
smallest stock size + reach of smallest clamp
and the whole origin thing is a pain --- front left corner would make the most sense, but it offends my sense of symmetry, and I find a centered arrangement convenient for some projects, and can usually work up workholding to as not to double any error from flipping things.
Phi appeals to my aesthetic sense, but didn't work out as well as I'd hoped when I did a radial arrangement of threaded inserts: http://www.shapeoko.com/forum/viewtopic.php?f=35&t=6045 --- that said, the PVC resulted in something pretty like to it.
I used MDF for a spacerboard --- plywood, even Baltic Birch as a bit too much variability, just seal it, or accept that you'll want to surface or use some scrap for a fixture before any project (I usually use a chunk of MDF: https://www.shapeoko.com/projects/project.php?id=154 )
I just worked up my own dustboot design: http://www.shapeoko.com/forum/viewtopic.php?f=8&t=3658 (since adapted to be a bit more universal ) --- there are a number of others: https://www.shapeoko.com/wiki/index.php/Spindle_Options