Are you allowed to perform "Short Field Landings" (=crossing the THR at 15ft instead of 50ft)? I have flown the XL/XLS for some time now and if you are right on speed (Vref, not Vref+5 or Vref+2!) over the threshold you can even touchdown in the normal TDZ and stop without problems, you just need to step on the brakes right after you are on the ground. But: you will have not much of a margin, but I guess you are aware of this.