I just finished a wool kilt in which I sewed the tapers by machine. Once you have the pleats marked out, then you pin and sew them one at a time. Also, I do NOT fold the NEXT pleat in before sewing as would be done with a handsewn kilt. As Steve mentioned, the pleat edge on top still has to be "scooched" upward a thread or two so when the stiches tighten the stripes will align. One pin just below the fell, two more pins up the taper to the waist, but the fourth pin at the top of the kilt does not taper.

***Practice with some scraps***
See how your machine and your estimating go.
***Practice it again***
Repeat until you know how it works.

Proceeding on, you will pull the pinned area under the presser foot from the back of the machine and sew it back out. Start above the fell and sew two or three stiches in reverse to the fell, then release the reverse and sew on up. This allows you to precisely anchor the fell line. Stitch slowly and evenly two or three threads in from the edge, taking out each pin right before it goes under the foot.

***Practice with some scraps***

Good luck.

w2f