Yep, "stitch in the ditch" is a great way to hide a waistband seam. The tricky part can be catching the inside flap all the way 'round. I find that either pressing and/or stitching the inside flap separately, beforehand, helps with that positioning. You can also place pins along the waistband upper edge, high enough that you aren't going to stitch over them (and so don't have to remove them as you stitch). Lots of possibility for bloodshed there!

OTOH, these casual kilts are almost always going to be worn with a belt, which effectively hides all that waistband stitching. . .

BTW, congrats on the first XKilt and here's to many more!