It's as simple as plumbing both tanks to a common tee. The trick is to keep the lines from the tank to the tee equal length so the flow resistance is equal. On my F-22 the tanks are on opposite sides of the fuselage. I plumb the two tanks to a tee and then to a header tank which removes any air from the fuel and then on to the fuel pump. I fill the tanks with a single line which goes to a header tank and back flows the fuel into the main tanks through the clunk. Both mains vent with equal length lines to a tee and then to an overboard vent.