I've been following his work since his 1973 VariViggen. Before that, he was a flight test engineer for the Air Force and also worked for Jim Bede doing the handling and stability work for the BD-5. While the BD-5 had a lot of problems (many of them related to the two-cycle engines), it was widely praised for it's handling characteristics. Since then, Burt has designed over 300 planes and actually flown well over 30. He knows a thing or two about flight test. He and his team are pros.

Burt's flight test philosophy seems similar to what Kelly Johnson did at the Skunk Works. Build - test - modify - test (lather - rinse - repeat) until it behaves as desired. When the Blackbird made its first flight, there were dozens of "open items" (known problems) with the plane. They flew it anyway and worked out the problems one by one.

There are several possible fixes for this instability at rearward CG condition. For example, they may lengthen the tail booms to increase the leverage of the control surfaces. They may increase also the size of the control surfaces themselves. This isn't necessarily a show stopper.