Thickness of wheel spacer isn't going to matter. The pinch weld mod is needed regardless. The pinch weld comes into play with such a large contact area on the tire during turning that spacer thickness doesn't matter.
Run whatever thickness you want, just be forewarned that thicker spacers place increasingly more strain on the wheel bearings and other hard parts. Also keep in mind that anything over 1.5" thick and the tires and going to stick out big time and look a bit ridiculous.
2007 Commander 4.7
265/70/17 Falken AT2, 17x9" Level 8 - Strike 5
RC Lift, Bilstein Struts, JBA 6.7s, Monroe LL's
AEM Intake, SuperChips Flashpaq