If it matters (it probably doesn't), as one who prefers the Randy Smith NV assy. over all others, and really doesn't care for the OS .35S type NV assy., I'd definitely vote for drilling the threads out of the case. Why? 1) The OS NV assy. has that danged clicker style ratchit bs that is a PITA to install. 2) The NV itself has an annoying failure mode when it is damaged (i.e., bent) and it
LOOKS ok, but in fact is NG and won't give any logical adjustments. 3) WHEN you need to borrow a NV Assy. at the field (because yours went Tango Utah), the odds are better that you'll be able to find a .156" (4mm) unit.
Steve