I thought I would post a picture of his bolt. It is actually a little difference as it is in three parts, I am keeping mine in two.
He has taken the outer bolt and chopped it in two, turning the head in to a key. The rest of the bolt is then turned in to a large grubscrew which is turned by the original head but moves in and out while the bolt head does not.
This is really for aesthetic reasons so the collimation bolt doesnt seem to move in and out from the telescope back.
I think when you get the length of the bolt right it is only going to move a couple of millimeters anyway so it wouldnt be too far from flush..
My telescope back is too thin to afford his design so I need to keep it as one.