@Merc
All I can say is it always worked for me, on more than one Amiga.
Your amigas have MEMF_KICK set on all fast memory then. In this case RAD is always in fast memory, regardless of what you do.
Setting bufmemtype to fast would allocate RAD in fast RAM.
No it does not. As I said already, bufmemtype has nothing to do with location of the RAD itself. It only affects the buffers used by the filesystem itself. And default bufmemtype of 0 is in fast memory already...