There has been an experimental version, built by Grumman, as Type X-29, during the 80s. I have only read about it in some specific magazines, but the tests were very successful, yet the program was so costly that it was killed after the cold war. If I remember correctly, the knack was about transferring the forces, and setting the position of the controls in situations of high angles of attack, which required a lot of electronic correcting in flight. Same with variable canards, it takes a lot of computating to match their stall characteristics with the main wings, and the sizing was problematic too. They are positioned closer to the center of gravity, thus requiring larger forces than conventional elevators, thus requiring more surface, etc... and again something brilliant that never passed the experimental status. Unlike the Russians, we had to account for our expenses.