Odd/additive meters (5/8, 7/8, 5/4, 7/4) have no correct single default and no way to author one

Additive meters must show their internal subdivision via beam grouping: 5/8 conventionally as 3+2 or 2+3 eighths; 7/8 as 2+2+3, 2+3+2, or 3+2+2 eighths; 5/4 and 7/4 analogously as 3+2/2+3 or 2+2+3/2+3+2/3+2+2 quarters. None of these is a universal default — the grouping is a compositional decision that must be visible in the beam pattern, sometimes further cued by a dashed internal barline between sub-groups.

Gould, Behind Bars, ch. Beaming — additive meters require the composer's grouping to be indicated; Read, Music Notation, similarly treats asymmetric meter grouping as an authorial choice, not a default.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.