The 11 series that I have are as follows.
311: 3.5" x .187"t 8" O.A.L.
511: 5.5" x .195"t 10" O.A.L.
711: 7.5" x .250"t 13" O.A.L.
911: 9.5" x .260"t 14.5" O.A.L.


So maybe the 1311 will be 13.5" blade, 18.5 O.A.L.
I'm thinking it will have to be .250" thick in order to fit the handles in stock.