My wife and I just bought new RR6, when I am going up a steep hill and am shifting down, when I reach my thumb up to the shifter to shift, often the throttle slips in my palm and I suddenly lose my speed and momentum. By the time I shift down and turn the throttle back on my speed is so slow I have to shift down into "2 & 1", and I waste battery getting my speed back up. Also, it's even more hazardous for my wife trying to shift down moving her thumb up to shift, loosening her grip on the handle bars, it's almost impossible for her to shift down. I think that I want to install a Shimano 7 spd Quick Shift under bar mount so I can easily use my thumb, will any Shimano 7 spd Quick Shift work with the existing Shimano Altus 7 spd derailer?