tuning broad heads to field points is not tuning your just making them fly the same.
Tuning would be bare shaft tuning and or paper tuning. Once you do that and then find that broadheads are not flying the same becomes a problem, why would one paper tune only to move things around to get broaheads to fly the same, your just erasing your tuning.
Sometimes they will never fly the same. then you either tune with broadheads or shoot mech.
But for me a drop away fixes all that. I never tuned anybow with a drop away.
Set it up properly with square and center point and start shooting field or broad heads.
Why anyone would choose a biscuit is beyond me, for 20+ years archers have tuned to keep any arrow or fletching contact upon flight now all of a sudden people are choosing full contact rests on arrow flight which is nonsense.