There are problems with putting two threaded holes in the flange.
1) They must be separated by some minimum distance to ensure that the strength of the flange is not compromised.
2) Given that they must go through the entire flange, which goes through the bottom of the camera, a larger hole is required in the wood, thus weakening it.
The Hasselblad holes are 1" apart on center, with the support spanning 2". That's a huge hole in the bottom of a wood camera.
Using a 3/8" hole with a 1/4" bushing when needed is much more sound from an engineering standpoint in this situation.