I would also seriously consider reworking your muffler hanger bracket. It's not going to hang there long from just one bolt, not on one of these vibrating 650s, lol. You'll want to fab up a 3 point mount with 2 attachment points to the muffler. Another trip to that scrap yard may get you some hanger brackets you can rework. The mounts from an earlier 650 or an XS500 might be good candidates. Their muffler mount holes are spaced differently in relation to the frame attachment point .....
I'm using XS500 mounts on mine .....
I'm using XS500 mounts on mine .....