9000 & 5000 singles are awesome. The double pedal versions are not so good though, the drive shafts have so much lag. The slave pedal is almost unplayable on some.
I've been using a 9000 double for the past 4 or 5 years, and I have to say I don't see this problem at all. I am not really a serious double bass player, since I rarely have the opportunity to play much music that requires it. However, I have a good right foot, and I've occasionally tested the slave pedal by playing it with my right foot, and I can do just about anything on the left pedal that I can with the primary pedal. Of course it isn't
exactly like the primary side - how could it be on
any pedal, since the slave side will always have to move the linkage. I think it's plenty close enough, though.
I have had a problem before, when there was some difficulty with the slave side, accompanied by some squeaking. That was just a normal issue with the lubrication, though. Just add some machine oil to the joints on the linkage, and the pedal will be like new again.