Joe, Here is my two cents. Let's begin with a few things that might assist you. One, make sure that if you wish to have the best reading from your bareshaft testing, make sure the target butt is at the same level as the bow. In other words, make sure you can shoot level, not down, or up.
The next thing, don't get hung up on nock left or nock right in the target butt. The question you should be asking is, when I shoot, do I see nock left, right, up, or down while in flight.
It is what the arrow is doing in flight, not what the arrow is doing in the target. Target material can fool you, they can give you a false reading.
I will leave my advice at this point, too much information can be more confusing. Give it a try, and move forward from there.
Scott