Coverhemming over a bulky serged seam is easy! I’ve been using this method for years. Don’t be afraid to clip close to the seamline – I haven’t lost a seam yet. :-)
Before turning up the hem, clip to the seamline at the foldline.
Then, turn the hem seam allowance in the opposite direction of the garment seam allowance before turning up the hem.
This will give you a nice smooth seam to stitch over.
Best of all, you won’t have all of those tiny, crooked stitches on either side of the seamline!