Black Sand switch verses GEB

Black sand switch just moves the whole discrimination range sideways a bit.
On normal sand it could cost you performance though on some bad land sites its will improve matters.
Ground balance is another thing thats not straight forward. On older machines all metal and motion modes didn't work to well on wet salt areas. You would use the TR non motion discriminate mode to balance out the salt ( at around the silver paper reject setting).
With a Fisher CZ 5 or 6 to get more depth on very small items on some salt beaches it was best to combat the problem by ground balancing by the bobbing method just as though you were on land. This could really add to depth but...here comes the drawback. If you didn't get the item out in the first spadefull of sand then the hole itself would also give a signal making pinpointing difficult.
The 6000Di was a good machine in its time and works fine on the dry but there's far better wet sand detectors out there.