I am having a hard time understanding how the seat angle is constructed in the pdf of the pattern. Point 23 is created by drawing a line through point 2 and some unnamed point, which I don't understand how to construct. It also seems like the center back line ends at a fixed height. Would the endpoint of the center back line not vary between somebody with a flat/larger behind?
Any help is appreciated.
Both the centre back and front will end up opposite from hem to knee. But I can't guarantee belong that. You will need to lay the crease lines on the stripe too.
The seat angle is established between pt 21 -22. Angle of the seat depends on the prominence of the seat.
There are three rises on a trouser.
The front Rise
Side Rise
And
Centre back rise.
The maximum length added to the centre back rise is 1 1/2 or 4cm.
It is correct to say that a flat seat would require less length as the seat is less prominent. 3/4" ot 2cm would be sufficient for a flat seat.