This method will add length and width easily and accurately.
Draw a line at bust level, from dart tip to center front on the cross grain.
Trace a line over dart stitching lines and seam lines down to waist level and up to front armhole notch.
Cut on line from center front to dart tip, along the dart stitching lines, down to waist line, and up to front armhole notch.
Locate the middle of the dart (fold line) and cut thru the dart between the stitching lines to the dart tip-but not thru the dart tip.
Make tiny snips to the stitching line but not thru the stitching line, which will allow you to pull and spread the paper where you see the dark blue lines highlighted with the red arrows. on photo below.
Spread the pattern to increase the length by the amount you need.
Pull the dart out, away from the center of the garment the amount you need. The yellow arrows show where you are measuring your increase. In this example the dart has been pulled back 1/2 inch and 1/2 has been added in bodice length.