Greetings,
Personally, I rotate the shell plate half way out of index.
The Shell Straps should now point to the index hole in the plate.
Back off the upper set screw about two turns.
Now, tighten the Filister Head screw at the bottom until it just touches the shell plate.
Next, tighten the upper set screw just enough so that the shell plate turns freely.
Gently is the key word here.
Repeat for the other two straps.
Last, insert a shell casing and check for movement and alignment.
Cheers,
Dave