I had SS rocker arm shims made in a .015" thickness.

These are to be used when installing rocker arm spacers, to help tighten up rocker arm side play.I use these to help center the adjusters on the valve stem tip, along with the .040" shims that come already installed on the rockers.

Rockers to be set with a .004" to .005" side play

Anyone that has installed the rocker spacers, are aware how hard it is to set them up with just the .040" shims.

These are $12 shipped for 16 shims, more than enough to 4 rocker shafts.

"EDIT"

Also, to get the adjusters centered, you may or may not have to machine the rocker stands. But with 911 adjusters, they don't have to be perfectly centered, but I go the extra stept to machine the rocker stands to center them.