I would use the TNT frame stiffeners for the XJ and just add some length. They also make a belly pan for the MJ. You only really need to protect the vitals which the belly pans do. Or you would just add some 3/16 steel or make another plate in a area you are worried about.
2008 3.0L CRD WK LTD - Wifes, GDE DPF Delete Tune, Turbo Resonator Delete, 3" Intercooler, Kolak Addcoo Front and Rear Sway Bars, coming soon 3.07 gears & SRT8 Wheels
2007 3.0L CRD WK LTD - Mine, Custom Spooling Tune - Stage 2 Performance DPF & EGR Delete, Custom Cold Air Intake , 3" Intercooler, Turbo Resonator Delete, DPF Delete Pipe, Devil's Own Methanol Injection, SM resistor plug, SRT8 rear springs, SRT8 rear sway bar; 255/70/17 Hankook ATM's, dechromed stock wheels
2003 F250 6.0L CCLB - Gearhead Tunes