Hey Bretto,
The hat channel that crosses directly below the gas tank has a threaded insert. The bolt is screwed up through the out rigger body mount and into the hat channel. This is the only mounting location that is done this way.
I am no pro, but probably a couple reasons for it. 1. A through bolt with a hex head under the gas tank is probably not desireable. It could rub and eventually cause a leak. 2. If you want or need to remove or lift the tub, you don't need to pull the gas tank to do it.
Tim
