Talk to a bunch of Grand Master shooters from IPSC or similar. I'll bet they don't hold it as tight as you're suggesting.
Of course you want a firm grip but that generally comes at about the same pressure as a firm but friendly handshake and with the same tension/pressure extended back through the wrists and forearms. If you've got that sort of support the gun will come back to the nearly the same spot just due to muscle persistance. I've shocked myself doing fast double taps on more than a few occasions where the second shot was within 2 to 3 inches of the first despite not actually aiming the second shot. But so far I only trust myself to do it in matches at 7 yards or less from the targets.
two uspsa grand masters/champions advice
"HOW HARD TO GRIP THE GUN
Brian Enos: “I’ve found over the years that the stronger I grip the gun as long as I’m still able to manipulate the trigger precisely, the better I shoot. In my book I talk about ‘relaxing’ when I shoot, and that’s caused a lot of confusion. I wasn’t saying you shouldn’t grip the gun firmly; I was talking about my overall attitude while shooting. What you want is a really firm, fluid hold on the gun. When most people grip a gun ‘strongly,’ what they’re really saying is that they’re using their arms and shoulders to bear down on the gun, so it just beats them around every time they fire it.
“My arms aren’t a part of my grip. I learned to feel the grip as only in my hands. That realization was a real breakthrough for me, that the grip is its own thing, not part of your arm position. Set up your grip without being in position, then push your arms out in front of your face without doing anything else to it; that’s going to be a pretty good shooting position for you.”
Dave Sevigny: “Grip the gun as hard as it takes to track up and down with the least amount of muzzle rise. If your grip is too relaxed, the pistol will recoil too much, track erratically, or it may shut down (failure to feed/eject, etc.). Gripping too hard, by contrast, may negatively affect sight alignment, induce trigger freeze (failure to let the trigger return forward far enough between shots to reset) for multiple-shot engagements and create fatigue in your hands and forearms. The pistol type and caliber will dictate how much actual grip pressure is needed.”"
i guess i was off in just saying without tremors, it should be "as hard as you can without tremor or effecting trigger control"