Stepper Voltage Enlightenment

Hey all, I did a test setting my Stepper voltages back near the default setting of .55 volts ( Plexiglass I3 w/ Nema 17's). I printed a 1 x 1 x 4 inch tower. The left is the result of the lower setting and the right is at .68 volts. The random ridges are .009 inches above the face and printed at 1.001 x 1.004 x 3.937 (in the good areas). The other is .9995 x .999 x 4.083. Obviously the higher voltage eliminated the step errors on the surface. I am puzzled though because my Z steps have always produced a shorter than expected final height. First time it's ever printed something taller (.083) than drawn. But, because I'm the only one in the world that has yet been able to talk to this Melzi board I haven't been able to address the Z step numbers. One other note, the left piece had a fan blowing on it while printing and is Flat Black. The other didn't and is Gloss Black. So, if any of you are having odd surface issues don't forget to check your stepper voltages.