John Y
Adam,
10mm is probably enough to annoy me as well. There is not a design problem or anything like that with these vehicles. But ware in certain areas can cause negative camber or mis-alignment. It would be very simple to work out what is causing this but you will need to spend some time eliminating each likely culprit.
Apart from a lot of obvious things like are the shocks the same length, are the springs the same, are the rubbers the same etc. Also look at the rear cross members/sub frame; the holes can elongate where the bolts go through that hold the trailing arms (see 65.35.20 of the Repair Operation Manual). Maybe not that easy to see unless the bolts are removed but the holes should be nice and round.
Check also ALL sub frame bolts are tightly secured and all sub frame mount washers are the same on each end as well.
JY