Best Bench Angle for Skullcrushers?

I think an incline for long head as this puts more emphasis on the stretched position. and a decline for the lateral.

The lateral and medial head are both attached to the arm bone. It seems like they would fire regardless of arm angle to torso. The long head would only contract if there is enough tension (by raising the elbows). I might be wrong but it seems all three heads would only be hit by doing overhead.