Mark & Juanita writes:
After considering this, I think it is also necessary to rotate the
router 180 degrees when doing pins vs. tails. When you look at
where the router bushing contacts the jig, it seems that you want
the same point contacting the jig for both pins and tails. To do
that, the router needs to be rotated 180 degrees. Would you concur?

No, because you want to consistently register the center of the
bushing against the same reference edge with the same offset. For
example, if your bushing was 1/4" to the left (assuming that were
possible), you want that offset to move the pins to the left *and*
move the tails to the left. If you rotate the router, you end up with
the pins moved to the left but the tails get moved to the right.

If the bushing has an in/out position error, you compensate for that
when you position the D4 rack after flipping it.

This assumes that the largest error in the bushing is it's position
relative to the router bit. Errors in the shape of the bushing, while
nonzero, are likely far smaller than the position error.