I infer from this that the CT extends into the wings, outside of the fuselage profile. An empty tank in the wing will very quickly cold soak. On descent, moist incoming air will deposit ice on the tank walls. Where is the outboard CT boundary?
At rib 8.
Rib 8 meets the front spar approximately at the inner end of the engine nacelle and the rear spar approximately in the center of the inboard spoiler.
CT volume is approximately 50% inside and 50% outside of the fuselage (25% on each side). The CT holds approximately 80 tons, which is 58% of the total fuel capacity.