It would be a 95mm tube.
Actually, I found something that said Vixen's own standard dovetail plate has central holes 35mm apart that match the Tak clamshell. Someone said that in the old version the holes are 6mm in diameter but in the newer "white" version they are wider and would take 8mm bolts.
The picture about halfway down this thread on CN seems to show this setup.
http://www.cloudynights.com/topic/51...df-vs-tsa-102/