Good job! They may go back Pakistan latter to design own stealth fighter after gaining more experience...Many Pakistani and PAF's officer engineer's are working in Chinese Aeronautical departments which also includes J-10 project and may possibly include J-20 project too.
PAF has history of projects with China in the field of Aerospace and Aviation. Someone said it right "Everything that is made in Chengdu eventually ends up in PAF".But what are they doing anywhere near a J-20?
If that is somebody from PAF.
Well J-10B has many requests of modifications from PAF.PAF has history of projects with China in the field of Aerospace and Aviation. Someone said it right "Everything that is made in Chengdu eventually ends up in PAF".
However, what the world sees is joint production/joint development between Pakistan and China. The projects like J-10 are considered to be 100% Chinese without involvement of any other country in development, production or sponsorship. However, there are engineers working full-time under the pay scale of Chengdu who are Pakistani and/or from Pakistan Air Force, employed by Chengdu. I know of one PAF officer who works full-time under Chengdu and is working on the J-10 project from scratch.
I am not saying PAF is certainly working on J-20, what I am is that there is possibility that PAF officer could be working directly on J-20 project (indirectly, yes).