Seat by feel. Not measured depth. Setting them below flus is just a given for safety.
The anviles feet must be bottomed out. If they are not then your SDs go up. Been proven over and over again in be chrest.
I've been seating by feel for more years than I want to admit to! When I started handloading back in the "dark ages" the 1st thing I was told was to make sure the anvils of the primers were bottomed out it the primer pocket!! I've never had a problem, unless I had a brain fart and didn't pay attention to what I was doing! Good shooting & be safe! Tuxedo007