As everything in life, sewing patterns are a balancing act-especially VINTAGE patterns!
After being folded for who-knows-how-long after having been treated who-knows-how by the one(s) who previously owned it and after warping the ease in the fragile tissue paper to create as careful a draft as possible, chances are a vintage pattern will be un-balanced at best.
When I first started drafting from vintage originals back in the 90's, I did so verbatim. That is, I drafted each piece as it lay on my table (after CAREFUL iron pressing) without matching the balance between front and back, side seams, etc.
Over time as I work in a multiple range of sizes via CADware, I make the effort to balance as much as possible.
A clear example is in a look back at the side-seam progress of the next pattern I will roll out (post-X-mas).
The example below shows the redingote sides front and back for a stunning 1943 ensemble (larger views are had by clicking on each)! The piece 'M' (side front) is shown in CAD lines over its corresponding underlay file which I drafted by hand from the original pattern. Keeping in mind this range of CAD lines was generated from the coat side back 'P', one sees how un-balanced the two are yet they must align perfectly to create a well-draped garment.
To achieve a better balance, I noted the difference between the lower edge of 'M' relative to that of 'P' (having matched the straight of grain in each piece) at 1-1/8".
When putting CAD lines down, I needed to add half that difference (9/16") to 'P' and subtract 9/16" from 'M'. Once I reviewed a test print of the CAD pattern pieces in the pattern's original size (44" bust), I was able to begin the grading process (as shown in a range of colors) having first graded 'P' and then mirroring that file to create 'M' so the side contours of each are identical.
Katrina Kay makes a good demonstration of balancing various points of your pattern (link here)-although her aim is in plus-size patterns, the process really helps in any un-balanced pattern.
2 minutes, 30 seconds in she illustrates what I am talking about here taking you further into centers front and back, armseye, etc.