Gyumin

First off, I'm the type of guy that tries to do everything I can on my own before searching out specific advice for my own problems. I have an 05 RX8, love it to death, but I've had to do a ton of work on it, and now I believe I'm at the end of the tunnel. But I came across one problem that was a surprise to me, but explains an issue I've had.
My fuel gauge has never worked, never really bothered with it as it never was an issue, however on trying to fix a different issue I had to replace the fuel pump assembly to resolve a hard hot starting issue, I found the main fuel level sending unit FLOATING AROUND in the tank, the bayonet mount was not mounted at all! The unit was connected to the assembly, but not the top of the tank for some reason. what I need help on, is where in the tank it connects to! I've felt around in it to find the mounting point, but for the life of me I could not find it. This is a series 1 RX8, and I'm in the driver side (united states in case that matters) tank.
I could really use some help, as I didn't unmount it, and I'm not sure where TO mount it in the tank.