The Artsoft website seems to be down, so no access to the forums right now.
Just for fun try replacing the M48 with a G50, that seems to be the standard for the CSS spindle speed limit for a number of other controllers. Be careful, not sure what will happen.
N17 G97 S410 M3
N18 G0 X36.1 Z5.
N19 G50 S410
N20 G96 S200 M3
N21 G0 Z6.