If you check out Gollevainen's Quizz of the week, Jeff Head posted some pictures of an F-15 tech demonstrator that had been fitted with canards and thrust vectoring prior the the ATF. The canards on the McDonnell aircraft were also fitted with an extreme amount of dihedral to keep turbulent flow off the main wing, so as to keep that airflow attached to the upper wing surface, in order to achieve very high angles of attack, and very quick turn rates without departure of that airflow and disruption of lift. The J-20 has a very similar planform to the Pak-Fa drawings of several years ago. The Russians have gone with a simpler planform on the flying models of Pak-Fa, that strongley resembles Flanker and the Raptor, I say this simply to illustrate that both designs are promising, but when you commit to one, planform or the other there are strength and weaknesses. I personally think the conventional Flanker/Raptor platform is more agile and stealthy, there are others who disagree, the real chanllenge is to integrate extremely hign performance, in a stealthy low observables platform, that retains L/O even under loaded combat conditions. The results have been stunning, the failures have as well, but in the end the manned ATF is today and likely to be in the foreseable future an amazing tactical weapon defensively and offensively. We must not rely on almost good enough, when our opponents are pressing upward to the true "high ground".