on a mixte, the twin longitudinal diagonals attach at the rear dropouts,where the bike has its widest structurally stable girth to triangulate the headtube/steerer from lateral & torsional deflection, making the bike safer & more precise in handling and stronger & more reliable than by simply attaching at the seat tube. the mixte design's intended user was expected to value comfort & convenience over performance & efficiency .using a semi-rigid attachment of the diagonals at the seattube or in the extreme case of the peugeot,bypassing attachment altogether, allows a greater degree of vertical compliance for absorbing road irregularities by utilising the full length of the tubes as spring members functioning under compression.