Your right--coil holes,,,this dam cell phone ,,,lost my regular ISp,,so Im temp, posting on it,,now that I think about it,,he would most likely have a real cogger with metal in the coil holes--being that it's a single phase alt with mags covering all the coils,,metal backing should work fine,,,your alt sounds on track,,,wire might be a bit light ,,16 would give more amps,, okay this typing on a cell phone is driving me nuts--later,,😜😜😜