Excellent photos; not so great on the math. Your reported .050" offset is not from the centerline; you have doubled the actual offset.

With no convenient reference point and no drawings, we can't know whether the hole and/or step down in the stock nose are mislocated (but if they couldn't manage to drill a hole perpendicular to the stock centerline, it doesn't exactly inspire confidence). Add the .025" skew in the hole location to the +.010" tolerance on the spring length and I'd guess by the eyeball method that you're approaching what shows as a gap between rear edge of band and stock step down. Distance from 'D' cutout in the barrel band to rear edge of band figures in too. Proper angle on the spring really matters if the wood has shrunk a bit from sanding.