Food for thought... The old Bear Razorheads were designed with bleeder blades, designed to break away if encountering heavy bone. The rationality being, you had an entrance "hole" instead of a "slit" reducing any pinch on the shaft, that could possibly retard penetration. Without hitting bone, you would get an entrance "hole" AND an exit "hole". If bone was encountered... You would get an entrance "hole" as the broadhead pierced the initial skin & meat, the bleeders blade would break away, and the arrow penetrating the other side, leaving an exit "slit". If by chance, the arrow encountered heavy bone, STOPPING penetration, you would still have a large entrance "hole" resulting in a "sucking chest wound" resulting in the rapid deflation/collapsing of the lungs. HOPEFULLY leading to a short recovery!!!
The Zwickeys do not have "break away" bleeder blades. In fact, they are VERY STRONG!!! What they do have though, is a proven track record, over MANY YEARS, as a very reliable broadhead with countless successful kills!!!!!
Whichever Zwickey 4blade you choose is up to you? They will all work just fine out of a 45# bow!!!