I did a pinstripe kilt for Tom to wear to the MSM. The stripes ran vertically along the fabric, so I cut and stitched pieces together to make them vertical.
The hardest part in such a project is matching up the tartan with each added piece. I found it easiest to match up the front of the pleat, as you would a regular pleat, then pin and sew the fabric inside a pleat.
I just added some fabric to a Cape Breton grizzly cut I'm making at the moment and used that technique. (Who'd figure a 36" hip kilt would need more than 5 yards?)