I have found that adjusting the reed gap on all six reeds in holes 8-10 makes for significantly easier bending up there. I adjust the gap to the point where the reeds just clear the reed plate. That is, to where if the gap were closed any further, the reeds won't play at all. This allows for high bends with a minimum of air pressure. It also makes the sound coming from these holes, bent or not, much warmer and mellower.
I'd like to know if that's what Filisko does to allow these same reeds to be overdrawn. Anybody know?