Just a note to anyone who might be interested. I have got the TS 590S running remote using the Kenwood ARCP program. The control program controls every aspect of the radio and does it extremely efficiently. HRD does not provide the same functionality or speed. So if you have the TS 590 I highly recommend trying the (free) ARCP download.
My initial experimentation was using a Yaesu 857 with the remote head . That was easy but wasn't all the radio I wanted (no tuner, no receive antenna etc.) The 590S with ARCP is just as responsive... really a very nice solution.