You might get away with a maximum of 20MB/sec transfer rate, but it varies depending on which CPU you're using and its speed. The disk speed is only relevant to the hard drive itself allowing the ability to transfer more data. Bus speed is more important than disk speed, however, disk speed is good reference, but only limited to the transfer rate the Amiga allows. Also, when you set up in HDtoolbox, make sure the maximum transfer is set to the ability of the hard drive, not default settings.
Hope this helps.
:-)
