What ever makes you happy really! If how the broadhead appears in your sight picture while aiming matters to you, then accommodate for that. If it does not, then you have every option....so long as they spin test true! Myself, I lean toward horizontal as much as possible....my arrows dont hang off the shelf but 1.5 inches and I just like knowing the cutting edge is not perpendicular to my bow gripping index finger...that just puts me a little more at ease is all. Also, I can see the tip of the head a little more....gives me a better peripheral in regards to what is going on. If I mount the head and its spins truest a little left or right of dead horizontal, thats where it gets epoxied to the insert. Broadheads or fieldpoints in flight and point of impact...no difference for me! Ive been shooting mostly Ace standards. Some Simmons as well!