How Tillman IV-2 fits fifteen 18-inch guns

How could Tillman IV-2 carry fifteen 18-inch guns and make 25 knots at about 80,000 short tons?

Its great length provides volume, while moderate speed, narrow armour coverage, and a limited secondary battery save weight within Panama Canal dimensions.

The design finds room for its main battery through enormous length, moderate speed, narrow armour coverage, and a limited secondary battery. At roughly 297 metres, it would be about 35 metres longer than Hood, with substantially more internal volume. The Panama Canal locks fix the beam and draft, so the designers exploit length rather than an unrestricted hull envelope. Its paper performance comes from identifiable compromises rather than a hidden jump to a 130,000-ton hull.