Some Call Me Tim: They didn’t go to all the trouble of acquiring such an impressive collection of syllables (see: Overly Long Name) to have some git go and shorten them.  Use all of them.

Well, at least, use everything up to and including the attributive name if you aren’t just going to go for the extremely respectful address by name-and-honorific alone.  If you are privileged to use personal or attributive name alone, you’ll be told so.  (And, no, reciprocity cannot be taken as implied, nor can it be extrapolated human-style from relative status.)

But they’ll never tell you a deliberately shortened version of one of those without meaning something by it, and you may not make one up.