X3 on the Rinehart target.
So much depends on arrow setup as to whether the BHs will hit exactly with the FPs. To me it makes sense that a BH might hit a bit lower due to increased drag over a FP. So if that happens, no big deal just adjust the scope. But if it's off in windage, then you need to look at the arrow. Things to try:
1) square the insert
2) align the spine of the arrows the same - try using a different cock vane
3) on a 3 blade head, align the clades to the vanes. A small rubber O ring sometimes works and keeps you from having to turn the inserts or refletch.
Don't assume your fixed blade BHs will fly the same as a FP Test everyone - at least once to verify.
All that being said, I shoot fixed blade heads over mechanicals all day
"Remember...always drink upstream from the herd."
Slick Trick Magnums, Magnus Stingers
BEA Exec and Zombies, Easton FMJs
2" Gateway Rayzrs
Boo String, DeerBoy Archery Strings