Hi Dave,
The 150ps versus 200ps difference is in my view only the result of the better RF-environment of the new relais(design) in the 015-0611-00 Pulse Head. I have both BNC Pulse Heads (311-01 and 611-00) and also their Manuals. Victor Silva has a 015-0611-01 Pulse Head. And this Tegam made one has the SMA-Connector as Output-Connector. I don't have a 015-0611-01 Manual (I can order one for you). According to Tegam's CG5011 Documentation the Trr is slightly worse (<160ps).
Greetings,
Egge Siert