Isn't the limit in J still 7kgs (total), even though you're allowed a 2nd item? In Y it's just one item. That being said I regularly travel with 2 carry-ons in Y, recently my rollaboard alone weighed 14kg. I was weighed on the onward flight on Indigo and they briefly tried to cause a fuss but then let me through. In J on EK you'll rarely have any issue however.