Leave Room for the Pilot

When equipping a mecha from scratch, make sure to leave at least two vacant equipment slots for the mecha operator's cockpit. (The cost of the cockpit is already factored into the mecha's base purchase DC.) On Large mecha, the operator always occupies two of the following three equipment slots: helmet, torso, and back. On Huge and bigger mecha, the designer has more choice when placing the operator's cockpit.
Copilot and passenger cockpits are described under Miscellaneous Equipment.