By "spin spot" do you mean the same thing as the "sweet spot", where the rocker radius changes?
I guess you are saying it is easier to stay balanced for an extended time closer to the center of the foot - right? Or is it just easier to control the initial entry?
Does moving the "spin spot" (and, presumably, the toe pick) back make it harder to jump, turn, check, or anything else? I.E., is there a reason it is that far forward?
I guess I could instead re-mount my current blades a little back on the boot, to get the same effect, but if was too much, the tails might sometimes cross, unless I ground off a little of the tail, which is an irreversible change, which I hesitate to do. Unless, perhaps I tried it with old blades that aren't good anymore for anything.
I've tried blades I got used, free, that were 1/2" shorter than my current blades, and I couldn't find anywhere to mount them that made it easy to balance, even for forward skating, unless I set them far enough forward that they dragged in the back, and slowed me down a fair bit. (But DressmakingMomma is only proposing a 1/4" change.)