Aha! My cousin ran into that problem once before! I had no idea what to tell him. Now I know.
Do you happen to know what geometry the newer winuaes are using?
And/or what is the maximum hdf size now?
Why doesn't a WinUAE .hdf have a few ULONGS of header information to describe the geometry being used? I mean its a virtual drive so it can do whatever it wants.
Do you happen to know what the value of MAX_CYLINDERS is under OS2.0+ ?