I'd say the more substantial issue would be fuel. A Federation Starship would have to carry enough fusionable matter (presumably deuterium) and antimatter to power the ship for a sustained voyage.
Shaw, your drawings are very illuminating. Looks like the TOS Enterprise must've stored a significant quantity of fuel in the forward half of the warp nacelles, and also some reserves in the outboard compartments of the saucer and secondary hull. Maybe it's time to assume, unlike TNG, that fuel storage aboard a starship is decentralized to balance the ship's mass. (It would make sense to store at least some fuel in the saucer for the impulse engines and photon torpedoes anyway.)
Shaw, your drawings are very illuminating. Looks like the TOS Enterprise must've stored a significant quantity of fuel in the forward half of the warp nacelles, and also some reserves in the outboard compartments of the saucer and secondary hull. Maybe it's time to assume, unlike TNG, that fuel storage aboard a starship is decentralized to balance the ship's mass. (It would make sense to store at least some fuel in the saucer for the impulse engines and photon torpedoes anyway.)