My Waist measurement is 40 5/8” and Seat measurement is 41 4/8” resulting in a Drop of 7/8”. I have drafted my trouser pattern based using the 1” drop adjustment shown in the HTA drafting book (Page 24) and I have also made the bow leg adjustments (Pages 17 & 18) and also removed one of the darts for a flat seat. My trouser pattern is shown below. When I take the Seat measurement off this pattern I get 46”, which is 4 4/8” larger than my seat. Rory said in his video that the Seat measurement off the pattern should be about 3” larger.
I was wondering if the reason for the seat on the pattern being too big was that I haven’t made an adjustment to the underside to take into account my 1” drop? Can I make this adjustment by bringing in the side seam on the seat line by 1 4/8" and then joining point 14 and point 25 to this new point?
You may not have done anything wrong. The system does have its flaws. When the measurements are further removed from the base size there is an issue with the seat increasing beyond the standard 3". Same goes for drops above 6", the seat can often come out too small.
What I would usually do is scoop out some of the excess through the side-seam of the undersides and keep the topside side-seam quite straight.