Currently I flying S3. The main question is which wing tab should be omitted (from top).
What the guy above said, but in my years of hooking up lots of old bird-man suits (classics, gti's, and s3's), it was usually the 3rd or 4th wing tab (counting from the top) which was skipped for almost any rig out there. 3rd was more common.
Have someone stand behind you when you are fully geared up and lift up your rig until your legstraps are pulling on you hard (to simulate hanging). If your laterals are touching the tabs on the top side of the opening (and creating tension in the suit), then you can tear tabs out when your canopy opens (bad). The fix for that would be to move up a tab (but chances are you are ok on the 3rd tab). You can do this test yourself with a mirror, or without if you know what to feel for and are flexible, squat next to a bench and let your rig rest on it. Hope that makes sense.