Craigosh-
The length between the wing screw and the front of the wing mount is 34-35mm.
The front of the wing mount (where it screws onto the tower) is not exactly round, but it's approx 7mm in diameter.
BTW my Dark Impact webpage has blown out to a full (albeit small) site.
You can check it out here:
http://http://web.aanet.com.au/fir/dark/index.htm