Classic Mini ... Does the gas tank really simply HANG on that strap, with the neck thru the body?

I replaced the rear shocks and following the Haynes manual, drained the gas tank, loosened the strap and slid the tank to the right in order to get to the shock tower bolt behind it.

Now, I've got everything back together where it looks right, but there's a rattle I didn't have before.

I didn't notice it until I started putting things back together, but I have a large magnet on the bottom of the tank which looks like it could be a spacer between the tank and the boot floor??? But when I wedge that magnet in there, the strap doesn't fit quite right and I still have the rattle.

I realize the rattle could be the shock tower bolt and I need to take it all apart and try again, but I'm wondering if that magnet is really intended to be there or if its just something left behind by a previous owner.

 

I don't have a magnet under my tank. I wonder if someone placed it there to pull/hold rust particles from inside the tank so they wouldn't enter the fuel line. Could it have been on the side and slipped when you moved it? Mine did not rattle after I installed new shocks. Could it be the arm inside the tank. Did you refill? Just some thoughts. Good luck!