Well the X weighs approx. 7300lbs with no one in it. on my V-10 with its 8900lb GVWR that gives me 1600lbs of CCC. I`m not sure off hand but I believe a similarly equipped 250 is rated at 9500lbs (just below a cutoff of the 10k rating). and with an F250 being lighter than an Excursion by almost 600lbs that would give you approx. 2800lbs! maybe a bit less. I have the actual numbers somewhere from a V-10 F250. The Excursion is based on the 250/350 with 2 big differences. the frame behind the front seats is built differently to handle the body of the X and the springs were made softer to give it the mommy ride Ford was after when they built it, as well as making it lower to fit in garages. everything else is Superduty.
I run airbags on my X and it handles my 9200lb TT with no problem.