I hate to bring up old subjects, especially ones I took a shot at before, but let me try again.
I just heard the term "slip stroke" for the first time, and I am wondering if it is related to my stroke. Over the years I developed a stroke which employs a very loose grip with definite wrist action. I do not allow the cue to slip, however, and I now apply beeswax to my wrap to keep it tacky and prevent my cue from slipping from my hand and my throwing my cue down table (without wax, it happens). It is my belief that a loose grip and wrist action greatly contribute to spin/english. I have also found that when I grip the cue tightly, it kills CB action.
I am particularly interested to know why a loose grip will fire a CB up and a "death" grip kills CB action.
Note: I am not a physicist, not a great player and the following post should be taken both with an open mind and with a grain of salt.
My guess is that with a "death grip" you're unintentionally treating the pool spheres as if they were 2D flat objects. You're pushing the tip through as if it were a flat surface. Loosening your grip equates to the sphere being treated like a sphere. (EDIT: and as a result contacting where you mean to) The tip contacts the spherical ball in a more natural motion, instead of trying to push through it at an off angle. Imagine when a miscue happens, I'd be willing to bet it's easier to miscue with a firm grip unless you're also accounting for the spheres being spheres and have a good stroke. With a death grip and a dead straight stroke, you're probably pinching the ball into the table some, or at least flirting with a miscue, good thing we have chalk. Think about this, when we miscue, it's usually on a hard (stroke, not difficulty) shot, and on a hard/fast shot we are probably gripping the butt tighter than on a finesse shot. I know I'm more apt to miscue on a break shot than on a tiny shot to float a ball in at pocket speed.
Loose grip should allow the tip to deflect off of the cue ball, reducing any unwanted stroke flaws. If you push it through tight, I feel as if any flaws will be magnified. I've found that many good players who have minimized their flaws do indeed have a tighter grip. The whole "dead level loose grip with follow through" that is preached to beginners has reasoning behind it, it's harder to mess up while shooting like that, though it is in a way like training wheels. You'll never lean into a curve and turn that small radius if you have training wheels on.
If you are ever close to a rail and HAVE to put draw on, you might notice you swipe the ball a bit, kind of a parabolic motion. You're definitely not treating the sphere as a 2D object. Look at the players with "natural" type strokes, especially the Filipino players. They stroke the ball, not only dead straight, but sometimes in a parabolic motion. Look at this:
Bustamante definitely strokes the ball great, but look at how he addresses the cue ball, as if it were a 3D object, not a 2D one. His stroke is absolutely beautiful, it's more exaggerated than most, but when you're hitting good, this is the kind of feel you get on the ball, not just poking a 2D object. If a beginner addressed the ball like this, an instructor would probably have a fit.
I'm not completely suggesting stroking in a parabolic motion, but it's a nice thought experiment. I'm sure if you get into the micro level of things it all has to do with how the tip glances off the CB but I have no idea how to confirm that. I guess what this long drawn out mess I've written is saying is, if it works for you, do it. There's nothing wrong with a loose grip, but once your confidence is up, try tightening it up and see what happens. Try it every once in a while.
EDIT: If a tight grip is killing CB action, I'd be willing to bet you're stroking it like a stop shot. You can make the cue ball stop even if you hit it above the equator... hint the entirety of your cue is also a 3D object which can pivot. Again, a loose grip diminishes any flaws along with the fact that tight muscles take more work to control than loose muscles.