Hi, this is my first post on this great forum so I hope it will be useful
I think the problem is the "D" dimension in "mounting holes dimensions diagram" on previous page. S2 type has D=14.8/17.3mm and S3 only 7/9.5mm, which means that mounting holes for S3 type on frame are closer to chainrings. So if frame is designed to use S3 type (and I don't know if ip256sl is) and you use S2 type derailleur the same problem as yours shlould emerge. But I must say I have no practical experience with this situation, it is only my theory  .