Exchange of SRA Flat in Mumbai in the same building

Hi, We have recently allotted an SRA flat in Mumbai in the month of November'16. The flat is in the name of my mother on 15th floor. Also in the same buidling my maternal uncle has also been allotted a flat on 13th floor. We both want to exchange the flats within ourselves. Kindly guide me, how I should go about it or a provision is available within SRA rules wherein family members can exchange flats within themselves. Also the documentation process...