Slightly off topic, I have noticed that some on-line parts houses have started showing all dimensions as metric; that is, they list 318cid as 5.2L, etc. That's fine for engine displacement, but they also show wheels, brake drums and hubs with dimensions converted to metric and rounded off, which is basically what that ATV chart did. So you see mixed-dimension absurdities listed, like "9-inch brake drum for 5x100mm wheel", which is nonsense -- such a beast never existed.
On the current debate, it seems to me that cone lugnuts would not distribute the load equally if each one is not absolutely concentric with the hole -- this, of course, is impossible, even with a mere 2mm discrepancy. Studs are not designed to withstand asymmetric side loading. And without a perfectly-sized center register, there would be no guarantee the wheel would mount perfectly centered on the lugs -- even one millimeter off would probably cause a vibration.
If you had an alloy wheel, with enough meat to be redrilled, and use the mag-type lugs with the sleeve that fits the hole precisely, that would be no problem. But I can't see any cone-type lug being satisfactory. Sure, you can get away with it if you personally align and tighten each wheel carefully by hand. But is your daughter competent to do that? You know the corner garage or alignment shop isn't.
