It appears from the forum that the 325 DMT is a bit aggressive right out of the box for maintaining an already lapped Norton stone. So a DMT-D6C is 325 grit. The DMT-D6F is 600 grit. So would 600 be ok for maintaining a lapped surface? Basically just cleaning up and prepping the stone before each use. Should I go with the full 6X2" DMT or the credit card size?