I’d like to share a mod done to my bike, a Trek 2.1, by my LBS in hopes that it will help others. Several years ago, I suffered a multiple root avulsion from the brachial plexus that left me with diminished use of my left hand. I can maintain control of my bike with my left hand. But, to use the left shifter on my bike, I’d have to reach over with my right hand and pull the shifter. This was not optimal and I almost lost control of my bike several times.
My LBS, shout out to Race Pace Bikes in Columbia, MD, suggested adding a Paul Thumbie and new shifter to the right side of my handle bar. I love this setup and it I no longer fret when I need to make those big gear shifts.