Not sure what normal or average is but after a lengthy dialog with Mike from the bootfitters group,
My height is 5'8" . In bare feet, if i measure from the ground to the top of my knee cap I measure 21"
Mike took the same measurement on himself. He is 5'11" and his "tibia measurement" is 20"
While this is not the gold standard or an exact measurement (I don't have xrays of my tibia, only my femur) Mike and I have agreed that my Tibia is indeed long for my height.
So on top of the knee being further forward thus moving my COM further forward, the other effect it will have is I have longer levers to press on, thus amplifying the force or effect I have on the boot cuff. Also something else I did not know is that boots are designed and built around the assumption that the average foot size is 26.5. Geometry designs are not changed when the boot is smaller or larger. I am in a 25.5 so a shorter boot will have the same angles but a shorter base of support also amplifing the symptom of feeling like I was too far forward. Add in delta of bindings also designed with a "longer" boot in mind. Shorter boot means even more "ramp"
Bottom line is it took some experimenting to get me dialed in to where I am .
Is it perfect? Probably not. But it is working for me and that is what matters at this point.
It also helps me understand this a great deal more so I can apply this knowledge in teaching as well as assisting others.