The series resistance is NOT the resistance of the woofer. Its the resistance of the wire and terminals and connections along the way between the amp and the woofer.
WinISD Pro puts an initial value of 0.1 ohm and that's a pretty good guess. 4 ohms is nowhere close and its messing up your sims. With 140L, 17 inch (effective) port length (18.5Hz tune) and 0.1 ohms series my sim reaches Xmax with about 220 watts at the highest excursion point above tuning - about 28Hz.