I like the term 'fat-precision'. So if we have fat-precision binaries where single and double precision versions of an external class or lib are linked together, 'legacy' (well, current) Pd would refuse to load the single precision part, because it comes across a function <myclass>_setup64() which is unresolved. Unresolved means it can't find the definition, right? And we can't provide a dummy definition for this situation, as that would get in the way of the definition in precision-aware Pd. Hmm. This defies the purpose of fat-precision binaries, where Pd users don't need to bother about precisionness of externals.
Katja