The FRJ is the only full manual that I can consistently downshift without getting those very brief micro-lockups. I can do it perhaps half of the time in other cars. It's very difficult to get things just right.
Have you tried the new engine braking setting? Raising it reduces engine resistance when off the throttle, which can help keep the rear more stable when downshifting, especially if you're no good at heal & toe. (Like me.)