Manual was sent to you.
The KISS-SSB is a good radial ground system. It, alone, attached to the tuner ground lug should set you in good stead. You can, of course, add to the RF ground system, but most users find it's not necessary.
The wire from the tuner to the backstay antenna should be GTO-15 highly-insulated mono-conductor wire (same type as used for neon signs). Be sure the coax between the tuner and the FT-600 is good, with clean, tight connections. If there's any doubt, replace it.
Power for the radio should be taken directly from the house batteries via AWG6 cables
, with ANL or MRBF fuses
on both the positive and negative cables, located very close to the batteries. This helps ensure good clean power to the radio and it reduces RFI...both ways, from the radio to other instruments and equipment
, and from other equipment
to the radio.
Good luck. Have fun...the 600 is a great little radio.