Synodontis angelicus get almost a foot and are a riverine cichlid. They are effectively able to protect themselves, but not nearly as well as clown loaches would. Bristlenose plecos aren't any better able to protect themselves than any other pleco. Loricariidae in general have odontodes that they use to deter attacks. Withstanding the aggression they deal with in cichlid tanks is more a case of being tank raised for generations and having less stress factors so it increases their survival rate, IME.
Anyone that has loaches getting too big for a 90 gallon tank will have NO problem getting rid of them. They're in huge demand. People try to buy the ones in my 240 gallon on a weekly basis.
Barbie