Actually, I was planning on running a main trunk on the ceiling to the
planer/jointer/table saw, having another drop for SCMS, and running a line
along the back wall for that. *Simple and straight.

I have a DC that uses 6" pipe also. I to use pvc to avoid the cost on
complexity of metal piping. Was indeed worried about static sparks,
etc. I did a lot of reading and ended up using 6" irrigation grade
pvc, can't recall schedule. I also applied metal tape along the
length, inside and out, even through the fittings so I have ground
running from every machine all the way to the DC. I have never even
had dust cling to the outside or ever seen a spark or any evidence of
static build up.