I use the same setup on 3 bikes but haven't had any issues like that. I'm sure hand size, grip design, and even setup may come into play. I'm also wondering about your lever reach adjustment...maybe out too far? From one statement in your post, it almost sounds like you're not aware that the Juicy's have a lever reach adjustment. I have some Juicy 5's on an SJ FSR.
If everything is set right on yours, you may just not be a good candidate for gripshift.
If everything is set right on yours, you may just not be a good candidate for gripshift.