I use a strip of light weight interfacing on the inside seams of leather or hydes. It will protect it from the feed dogs. You can leave it in where it doesn't show or remove it where it does. It also helps to glue the seams together. You can stitch right through the glue. It does not stretch as much when it has been glued. I have just altered a leather vest that I had to top stitch around the armholes. I glued the armhole seam to the inside and then arranged the lining at the armhole. I used the interfacing strip inside the seam where it was glued. You only get one chance to top stitch and it worked out really well. I used a regular needle sz16 to top stitch. Go slow and be sure to keep the article flat as you stitch so that bunching does not occur if you are not doing a straight seam.