Here is an old thread on the three line business with some photos. I didn't know of a gray Swaty. My HAD kicked up a little but I think I can live without it. :) Too darn many to get all of 'em.
I have lapped a couple of Swatys with the 325 and it is a long trudge uphill. I didn't ruin my plate but I am going to get one of the XX plates for the tough stuff and to lap stones that haven't been previously flattened.
For awhile now since reading ChrisL's method of lapping barber hones I've been thinking of doing a progressive lapping starting XX and then going to the D8C and maybe follow with the D8F. The F is my flattest diamond plate according to my straight edge. If I did the progressive thing I probably wouldn't have a risk of ruining any of them. :shrug: