Check the catalog here. It clearly states that it is tig welded. I assume it's because it is made from oversized tubes and there were no lugs at the time to handle them...

Frame sizing...My GF's Cannondale "Black Lightning" is a blast to ride and it is really close to an optimal fit for me. 50cm C-C seat tube w/a 53cm C-C toptube and 90mm stem. A bit of a strech but enjoyable non the less. My Bianchi is just about 52cm C-C square with a 100mm stem and a fist full of seatpost showing. Just slapped it together with junk parts to see what it would look like and rode it...Like a glove and tons of fun!

It's the 56cm top tube...Just plain weird IMO. I think the over sized tubes contribute to the lameness of the ride quality and lack of response. It would probably be just fine as a grocery getter or light touring camping bike but it's a RB2...Doesn't that imply that it's a pretty decent roadbike? I think so.

I'm blaming Grant! He probably thought it needed 38c tires and a short technomic raised 10 inches above the saddle to make a good bike out of it....Hate it!