Cut out your right front (1) on the slant, making your chevron as steep or shallow as you wish.
Use the right front piece you've just cut, rather than the paper pattern, as a template to cut your back left (2). Use it to get your stripes in exactly the same place.
Cut your left front (3) by placing your pattern piece roughly as shown and use your back left piece (dashed section) as a guide to where the stripes exactly go. Manouvre it a bit to make them match.
I'll explain about the waistband in the next post ...