Hi, I have a 59cm Tommasini Diamante that has the MS tubeset that you're discussing. You're right in
mentioning that it was a bit ahead of its time. All tubes except for the headtube have been
manipulated. The frame has proprietary lugs and requires a 25mm seatpost.
The bicycle rides like an absolute dream. The Tommasini geometry is very interesting. Its laid back
meaning that its great for very long rides, yet it has an extremely short wheelbase. As I recall,
its in the 97-98cm range. The tubing manipulation seems to have paid off as there is very little, if
any, flex in the bottom bracket area.
Its been a wonderful bicycle however I'm currently separated from it as I've recently moved and its
back in Indiana in the basement at my In-laws. 🙁
If anyone wants to see photos, I have quite a few available...