Another way to go about it would be to shorten the fork at pt2. Rather than using a 1/6th scale, you could use 1/8th.
This would then change the front angle at pt5.
So you'd be left with 5/8" at the side seam, 5/8" at the fly, and 3/4" at the front dart. That makes 2" and then subtract 1/2" from the quarter waist of the undersides.
The straight leg draft shown in the video series does give away the two other main leg figuration of closed and bow. Closed follows closely the drafting instructions of the straight leg, but bow is out on its own.
If it was only an 8" drop, the difference of the quarter waist would be 2". Which would work perfectly with the instructions above.
Another way to go about it would be to shorten the fork at pt2. Rather than using a 1/6th scale, you could use 1/8th.
This would then change the front angle at pt5.
So you'd be left with 5/8" at the side seam, 5/8" at the fly, and 3/4" at the front dart. That makes 2" and then subtract 1/2" from the quarter waist of the undersides.
The undersides fork would then be 1/6th scale.
The straight leg draft shown in the video series does give away the two other main leg figuration of closed and bow. Closed follows closely the drafting instructions of the straight leg, but bow is out on its own.
Let's say the waist is 30 and the seat is 40.
The difference is 10".
10 divided by four is 2 1/2"
You can take 5/8" at the side seam, 1/4" from the fly and 3/4" from the dart. That's only 1 5/8". That leaves 7/8".
This 7/8" could be subtracted from the quarter waist of the undersides.
That could work.
The menswear draft is set out as a 6" drop even though most men would be 4 or 5. The idea behind this was to make the 'difficult' one the standard.
Women are similar.
If I did out a womens wear draft, I would probably make it a 10" drop, even though most are only 6 or 8.
The difficulty in any draft, aside from leg figuration is the drop.
The quarter waist is governed by the quarter seat.
You can use the same drafting system. Just like menswear, you'd select the draft based on leg figuration.