Happy1, I think you're in the right area by experimenting with the amount of Dead Band and Damping you set. On all three items (roll, pitch, and rudder), I set mine about 1/5 or 1/6 the way up from the bottom of the vertical bars, close to what you describe as your settings.
Oh, and I set all those other degree buttons totally up against the top limits. I used to try what looked like a slant line starting from about 10 on the left to around 90 on the right, but find that just leaving all of them maxed at the top works best.
My Logitech Extreme Digital 3D is still the best stick I've ever had, and I have no plans to replace it except with maybe the latest one that has more buttons (sounds like yours).