Yep, head flow numbers don't mean a ton to me unless there is a way to really document everything. I found this out years ago on my own bench when I played around with head placement over the cylinder. It is easy to pick up some cfm my moving the intake over closer to the center of the bore. I finally built a fixture with dowel pins so the head was always in the same location on the bore. I also machined up a radius plate that I used on all heads. Once I did that I was able to start getting repeatable results.

There were some guys on SpeedTalk a while back who had a test fixture which they sent from guy to guy so everyone could calibrate their benches to the same fixture. Something like that makes sense for people who are working back and forth a bunch.