>Another way to skin different versioning cats is to compile into COM dll, as the COM dll will load their own runtime - but at the cost of tenfold calling time due to marshalling across thread/process borders - can be critical if "Chunky, not Catty" rule is not followed ;-))

I think you meant "Chunky, not Chatty". In English "Catty" means something quite different ;)

I remember many years ago reading a Calvin Hsia blog post about improving performance of COM automation, which basically discussed this (marshaling). I haven't been able to find it, maybe someone else has better Google-fu.

I think that post would also address Albert Gostick's question in another thread.