Hey Bill - -
I did make a 1/8" backing plate, but did not use the gasket. I felt the gauge was good enough so as to not have to come off for a long time, if ever. I sealed it top and bottom and have not had one problem. I fill the tank until I can touch the gas if going on a longer flight, and have never been sorry for installing it. To this day, I am glad I 'closed the window'. I have not changed anything about it since I did it originally.
John Bender