I haven't dived a Santi and the DUI I tried didn't really fit me well, the Rofos I used in training was good but my Seaskin fits me well and I have no problems with mobility at all, for valves or for general cavorting. I have dived with a Whites Fusion undersuit and also just in 4th Element J2 base layers with no real difference in flexibility that I could notice.Can you reach valves? How good is the cut compared to a Santi or DUI?