Well, I'm going with the spacer sleeve option and have found a good local engineering firm to do the work, whose boss is a motorcyclist!
I now have the Marchesini fitting in the swinging arm OK but, there are NO bearings that Ive been able to track down that will fit straight in and allow me to use the std '93 900ss 17mm axle.
Std bearing fitted (ST2 I was told) ID = 25mm OD = 45mm x 10mm deep
So I would need a bearing ID = 17mm / OD 45 mm - big difference.
I found a supplier who had a bearing 17mm x 40mm but, it was 12mm deep and I would have to have some 2.5mm spacer rings made for the bearings and I wanted to at least use A standard bearing either from the existing or from my 900ss wheel design.
I've asked a couple of knowledgeable peeps and they can see no problem with this approach.
If anyone is ever so foolish to attempt this as well, the dimentions for the spacer sleeve are:
178mm long x 17mm ID x 25mm OD and I suspect it might need some final hand finishing to get the tight fit that is needed. I've asked for the sleeve to be made in Carbon Steel rather than alloy as this seemed a better option.
IS it worth the problems???
Well, for a perfect rear Marchi that cost me just over £100 I hope so - time will tell
night night - Frank