Alton Brown does this with skirt steak on YouTube. Looks awesome, is on my list. Brown recommends a little salt, more pepper, meat at room temp. 45 sec a side, then 15 minutes in foil if my memory is intact after 3 IPA's
I built a table for my XL and used the 12.5" dimension. It is right - I am using the table nest for support.
On a separate note, if you plant to use a table cover from BGE, hold to their dimensions - I went too long by an inch and it is tight. Can give you top dimensions and drawing if you are interested- a bit more detail than the drawing on the BGE site