hard mounted fuel tank

[bgd73]

I am thinking of warmer weather chores, sometimes make a list, think things out. I saved a unibody subaru, it was difficult.
I am second thinking the gas tank and its hard mount to the body. I find this rather strange. alot of unibodies do this.
I am welding the entire area where tank is in the back with tank removed and realized the body is going to be very very strong, I have gone beyond the oem "squishy" signals because of full differential lock in AWD. No excuses for me in the creakin moaning leaning and snapping..I welded until the epiphany of the minimal effects after a hit and run in the rear, on a steep hill in my locale. I made a mess of the all steel bumper before the rear quarters I made never bent..
Well, there is a safety concern, due to very strong steel with strong signals..and a hard mounted tank.

I am wondering what others have done with fuel tanks, fuel cells, custom made etc.

For now, I am simply going to run high grade gas proof silicone before install, on the seam. It seems common sense to be enough, but what of friction of silicone to body? should I use high temp? Open to ideas.