Sir, I've also learned recently that there will be two elements to the Stealth program in Pakistan. One would be getting the J-31 and Second, to build a platform internally called the JF-18, it would be a smaller single engine Stealth plane with different air-frame and tech, so like a mini J-31. While the J-31 will form the hi of the Stealth tier.
I, unfortunately, can't site the source as he is a friend of mine in the PhD program with a father in the PAF at a very high rank. So take this for what its worth. But when he tells me something, I've seen it happen and this very forum confirms he was right on previous stuff too. Thanks