I have a trick that has always worked for me.
It takes seconds.
I shoulder the rifle and look through the scope.
I twist the scope until everything looks good.
Then I tighten up the screws.
Simple but effective. Never fails.
I challenge you to shoulder it left-handed and see how level it is.
Why would I do that when everything is working fine?
You familiar with "If it ain't broke, don't fix it?"