Well, after almost losing this wheel, here's what I've discovered - the lug holes are slightly wallowed out. From the front side, the taper looks pretty good on all 5 holes, but here's how it looks from the back.
Now, the rim is hub-centric, so it fits flush right around the axle hub, and the lugs seem to have a good grip. I was able to torque them down to 100lbs. last night with no issue. I've only driven it a mile, and it didn't seem to have any vibration. Should I be concerned about this wheel?