Have not been able to locate the SM for the HR-S3500U or the 9500U but at least the
HR-S4500U and HR-S7500U shares drum assembly part number. The 3500U doesn't have the dynamic drum system but though it may very well share the rest of the drum parts with those. The 9500U has a flying erase head I think so the part no for the upper drum will be different, no idea to what extent there are differences between the actual heads on different upper head assembly part nos from the same lineup and tv system, not much info on it.
JVC tended to share a fair bit between the models in one lineup on their later decks in general as seen in the attached video technical guide for the 1998/99 lineup.