hey BC
this is just a thought,
but servU keeps it database in ServuDaemon.ini (v4), you could try to upgrade all 3, one at a time (so all 3 servers use same format in .ini file making everything smooth as possible
), then rename (1 at a time also) each to a diferent domain/server, and finally, just copy-paste from the 3 .ini files their domain/users section to only 1 .ini and test it (maybe) in a new server install (offcourse with full backups of everysingle1 before messing with it
maybe this is not so clear cause of my english, lol
just an ideia, dunno if it will work fine tho,
but if it's a large users database in each server, it sure is worth to try
also, servU is very popular, as you know
and many ftp servers develop companys are offering tools to import the servu user DB to a different server proggy,
maybe could try to contact the company of the future serv prog you want to use