hi Greg
i'm sure you're familiar with this but
if you use TSX, ideal method would be to install the ASCOM2xMount adaptor for TSX which presents tsx as an ascom mount.
http://www.bisque.com/sc/media/p/112531.aspx
but if you use tsx I doubt you'd need to use phd as guiding via the control plane with tsx is much better than st4 or relays.
so not sure what your interface is.
Cheers
Alistair