Recall there are two pieces of aluminum at this fitting location. One is the side skin and the other is the inside panel. I could have merely enlarged the hole on the inner panel and put this fitting in just the single outside skin. But I didn't. I wanted it to cover both pieces of aluminum.
So I made a big washer for the inside panel. I used the standard 1/8 big washers normally used with bulkhead fittings on the outside skin. But then I had to fill the little space between the plastic insert and the washer. This is thickness of the aluminum which is .032. So I made some 1 inch washers to fill that space.
It worked fine. I was able to torque this to 70 inch pounds per specs. All seems fine. I also used torque paste on the threads to hold it from vibrating loose. That should do it. Also when you put the hose on the nut on that gets close to the nut holding the fitting which gives a little extra protection from the nut coming off.
I'll use fuel lube when I eventually put these hoses and fittings together for good.
