Weird. I've got At least 7 sets of Slix Springs nipples spread out between pietta/uberti 1858's, walkers, pockets, 1860's & 1851's. They all work perfectly with CCI #11 caps.
Track of the wolf nipples also fit #11 caps well.
I don't have any regular RWS 1075's, but I have a ton of 1075+...