[fintubi]

Thanks, all. A couple of other thoughts:

• The QR hub is indeed super cool. But since it's typically supplied with the standard steering wheel, I'd expect that it's tapped for 10-24. So it would only address the issue if a new one is custom-tapped to take the Moto-Lita screws, or if 10-24 screws are used.
  
• The Moto-Lita hardware comes with locknuts, so they're assuming that the wheel will be mounted to clearance holes rather than tapped ones. The tapped holes in my hub are through holes, not blind - so if there is space for the nuts on the back side, it may be possible to open up the existing holes to clearance for M6 and dispense with tapping altogether. I'll have to examine the back side of the hub to see if this is an option.
  
• Lastly, I'm not convinced that there's any problem mounting the new wheel with the existing hardware. The old screws take up fine on the countersink of the new wheel; so as long as thread engagement is maintained nothing else has changed. That was really the original intent of my post: lots of people use the M-L wheel, so there must be a standard practice here. I'm aware of at least one other car where this wheel was swapped into a build at ERA; so far as I know, without any heroics needed.

B