I used the guidelines described in Threads magazine article: "Adjusting Pants from Waist to Seat" to make some of the needed adjustments to fit McCalls 5710.
First, I reduce the length of the back crotch by 1/2 inch. Then I removed 5/8 inch from the center back seam to increase the body space.
Next I added 5/8 inch to the side seam to compensate for the decrease in width.
The front crotch length was decreased by 1 inch. Above are the two pattern pieces side by side to show the body space area. Note the back piece is about 2 inches longer than the front. This compensate for the curve of the buttock and the sway back. Imagine the back pattern piece having flexibility to curve slightly as a sway back would.
Additional adjustments made:
Sway back adjustment of Back Yoke
Length the pants by 4 inches.
Stay Tuned! Finished pants post is next.