I run three different weight inserts behind the points on my Easton Axis shafts, 50, 70 and 100 grains. When I correspondingly match the difference with point weight, I get no difference in impact. For that matter, I can shoot them all with the same weight head and get very little difference in impact. Nothing that fletching won't clear up.
Sometimes we make this harder than it should be. Sure there are tiny differences depending on where the weight is located, but they're just not enough to worry about. A half inch, maybe even quarter inch, difference in draw, a clean release vs a pluck, etc., will produce more impact variation than whether 50 grains of weight is moved a half inch farther forward or backward in/on the shaft.