Pants fitting for a protruding derriere

I have a size-10 waist but a protruding bottom. The center-back seam of trousers always cuts between my buttocks. Can you advise me on how to adjust a trouser pattern for my figure?

—Janet Ayoola, London, England

The back-crotch extension of the average pants or pants pattern, replies Della Steineckert, cannot accommodate the additional fullness of your bottom. Rear fullness borrows the additional fabric it needs from any loose part of the pants. For instance, rear fullness will pull the center-back waistband down uncomfortably, particularly when you’re seated. Since the back-crotch extension of most women’s pants is too slanted and too short, this pulls the seam upward into the bottom cleavage. Using a larger pattern size is not the answer; larger-than-average fullness in any area, be it back, bust, bottom, or abdomen, requires a localized adjustment to add length and width.

Whether your figure is average or not, the fact is that the crotch curve of most pants and pants patterns does not conform to the profile of the female figure, and this aggravates any other pants-fitting problem. Compare the usual cut of the back and front of pants or pattern pieces with the profile of a typical female figure in the drawing below, at left. You can see that neither the shape nor the width of the crotch curves of the pattern pieces duplicates those of the figure. In short, the front curve needs to be shallower, and the back curve needs to be deeper to conform to the figure. The too-shallow back-crotch curve intensifies the problem of larger-than-average buttocks. 

Furthermore, the center-front and -back seams of many pants and patterns are too slanted and thus act as a dart. The center front should align with the straight grain, and the…