Hi,
We have a 7200 OS8.6 Mac set up as a print server using Mac Plot with G4 clients running OS10.2.6 and Mac Plot in Classic (OS9). Plotter is a HP350c with Microspot serial to parallel converter cable to the server Mac.
There should be a software application with Mac Plot which allows you to set up a server and the client Macs.
On the client Macs, the Mac Plot has a network driver showing in the Chooser.
On the server, a local connection method is shown.
Hope this helps.
Regards,
Nick