Roman numerals align under the beat/chord-change onset and sit at a consistent baseline below the system, in a fixed vertical order relative to figured bass/lyrics if all are present

Roman numeral labels are placed directly below the bass staff (or below any figured bass present) aligned horizontally to the note/beat where the harmony changes, on one shared baseline across the system. Gradus's recommended fixed below-staff stacking order, since no authority mandates a specific order: dynamics (closest to staff), then figured bass, then roman numerals, then lyrics (bottom-most) — documented here as a house-style decision.

Roman-numeral labels render at inconsistent vertical offsets from one system to the next, or overlap a figured-bass row when both appear (a real scenario in Gradus's curriculum, which teaches both over the same chorale excerpt).

General harmony-pedagogy engraving convention; Gould's general principle of consistent below-staff stacking for multiple text layers (/476) is the closest applicable authority for the coordination requirement itself.

This rule is about where marks land on the page, so it can only be judged after engraving. Collision and spacing faults live here.