The tank attaches to the main spar but the fuel does not go all the way to the spar. The ribs are slightly shorter in the tank than in the rest of the leading edge and they attach to the rear tank baffle that is shown in the first picture. The Z brackets in one of the earlier pictures attach to the rear baffle and ribs on one side and the spar on the other.

These pictures show the rear baffle in place so that you can countersink the holes in the skin that attach to the baffle. The skin is thin and the hole in the baffle stabilizes the pilot on the countersink bit. the last picture shows some holes countersunk and a couple about to be.