Close Bob. More like this:
You must shoot a lot of soft shots. Do you take a short backstroke? What about your follow-through? Does your hand eventually clamp down on the cue or are you gripping with your fingertips all the way into the follow-through?
It would seem to me to be an incredible amount of work to have to keep the cue straight on shots harder than medium-slow speed. Why work so hard? If other grips aren't working for you, maybe you should find out exactly what is going on rather than keep reverting back to something that could possibly hold back your progress in the game.