I do have some thumbies new in the bag and was going to try them until I figured out how to proceed with my Grip Shifts. I really like GS on upright bars. Barcons were a fallback choice and holdover from the drop bar days and they can be problem solvers at times. My old boss had a bum left flipper and his upright Witcomb was fitted with a thumbie and a barcon on the right side for him to be able to use his right hand to shift both the front and the rear derailleurs. You do what you need to do.