Got some work done on the XS over the last couple days. To mount the mono shock with the reservoir I had to remove the horizontal frame brace from the backbone to the tail section on the right side. That is also the lower mount for the right side frame cover. I do not have a way to bend tubing so I had to find a part that I could cut to fit with the correct bend already there. An old engine guard worked out well.
To reinstall the side cover the lower mount had to be moved forward on the cover. I tried to drill the spot welds holding the lower mount bracket without going through the cover.
Even with the mount removed the cover had to be modified on the lower side since the new frame rail stuck out further than the original to get around the shock reservoir.
With the lower mount moved forward and the bracket located on the new frame rail:
One of the things I wanted to do with this bike was to have 2 different tank and seat configurations that could be swapped out easily. The stock tank for normal and longer riding and a much smaller and lighter tank for short rides. The smaller tank ended up being an MX125 tank from an early '70s Yamaha. The front mounts are the same as the XS650 Special tank. It clears the tunnel with the exception of the coils (still need to relocate them) and the 3 piece upper motor mount (another mod still coming). The tank is much shorter than the original so a second rear mount had to be added while still being able to mount the original tank.
The mounts for both tanks are similar, a round grommet on the tank slides over a frame mount and is captured by a bolt through the top. I was able to use a modified lower suspension bolt I had with the YZ490 doner and weld it to the frame. It had to be short enough that I could mount the original XS tank over it. That part took a couple tries.
Now both tanks can be swapped out easily. The next stem is to relocate the coils.