you can just use a y piece and no taps, the fullest tank will preferentially empty and syphon into the emptiest so in effect they become one tank. fine as long as the tanks are next to each other, otherwise if one is lower than the other you will syphon into the lower one overfilling and spilling it.
It works fine with 3 barrus tanks side by side on my SR.
trouble then is no reserve........
I am usually not as green as i am cabbage looking.