There is often restrictions as to who or if a buyer can sell to a third party. And although the knowledge from thoroughly testing and evaluating an SU-27 or SU-30mkk would be helpful it would likely be of little use to PAF pilots if they ever encounter the MKI due to today's BVR arena, different avionics and different performance from enhancements such as TVC and canards. If Pakistan ever thoroughly evaluated the SU-27 or SU-30mkk the most knowledge they would gain would be in general performance, this includes roll rate, sustained turns, rate of climb ect, ect, but again the performance of the MKI is slightly better compared to base SU-27's and SU-30's; and the MKI has completely different (better) low speed performance.