I managed to finish my Lanesplitter skirt! I decided to line it with a poly/cotton knit jersey fabric and make a waistband at the same time, rather than knitting in a waistband. There are lots of ways this could have been done, but my objectives were to 1. make it quick, 2. enclose the top edge of the knitting, and 3. reduce bulk. In case you're interested, here's how I did it:
1. Wash and block the knit skirt. It's basically a large rectangle, and I measured it after it was blocked and before it was seamed.
2. Cut the jersey fabric the same width as the skirt, but 2 inches longer, making sure to orient the stretch of the fabric across the width. These dimensions mean that once the jersey is seamed using a standard 5/8" seam allowance, it will be just slightly less wide than the skirt itself. The waistband will use up 2-1/2" of the height, and the hem will use up another 1/2", so the liner will end up being about 1" shorter than the skirt.
3. Once the skirt and liner are each seamed, with wrong sides together, baste the skirt 2-1/2" below the top edge of the lining. Put the seam of the knitted skirt on the opposite side as the seam from the lining to reduce bulk.
4. Fold down 1/4" on the top raw edge of the lining, and then fold this down towards the right side of the knit skirt, enclosing the top edge of the knitting. Sew in place, using a topstitching foot if available. Leave a 2" gap to insert elastic.
5. Insert 1" elastic, adjust to fit, and sew ends of elastic together. Finish topstitching remaining 2" gap.
6. Add a 1/2" hem to the bottom of the lining, if desired. Since it won't unravel, you really could just leave it alone if you prefer.
More pictures on Ravelry.