the best heifer we had this spring was an "x",, born unassisted to a blue roan recip 88 pounds .. I would not use him on heifers or small second calvers
All my x calves have been mid-70's and unassisted. I haven't ever used him on a first calf heifer but if she has some size I think it would work fine. Heifers look better than the bulls from my experience