Not to detract from the OP's question, but:
I am still using the GP4000SII 's as well.
25mm on my Roubaix and 28mm on my Sirrus.
I've been very happy with them.
Knowing that the 4000's run "a little big" i.e. 25mm measure closer to 28mm and 28mm run closer to 30mm when mounted...
I've heard that the 5000's are closer to their indicated size so .... when I make the switch to the 5000's should I "size up" i.e. Run 28's on the Roubaix and 32's on the Sirrus?
(lots of frame/fork clearance with current 4000 set-up)