I don't get how if you only adjust your rest you can get the BH and field tip to fly the same. He already mentioned that his FP is flying perfectly. Any adjustment of the rest might tune in his BH but will then cause his FP to fly out of line.

I had this same problem last year with my arrows. My solution ended up being that I resighted the bow in for BH only so that they were shooting consistently straight at 20 to 30 yards. I couldn't shoot my FP again until I moved my sight/rest back to where my FP where shooting well. I probably had a arrow spine/tune issue which made my BH shoot differently than my FP.