I've seen similar pictures online, and that seems to match what I've seen on other 86 750's. Here are detail pictures of mine, hopefully you can get a better picture of how it's set up. I don't claim any credit for the design, just trying to figure it out by reverse engineering at this point.
The big tube coming out the back and up goes to the carbs. There's a support welded to the top that gives support.
Looking down and back from the front.
Looking from above the cleaner and tank, towards the front. You can see the support going to the left side of the picture.