A brooks is basically a hammock. If it starts to sag,instead of sitting on sit bones everything slides to center. Even if it doesnt look like it. It has enough miles on it to need like Machka said about a half turn,no more dont get carried away,a little is lots.. We all tend to be a little lopsided,im guessing with it sagging, its going off to the side your off on more than it normally would. My oldest B17 is slightly twisted cause im sure i am to. In fact my newer one is also going slightly same way. They are designed to mold to our way of sitting when reasonably stretched not sagging. Cheers.