Spear M · Arden S/M · ER:ONE S/M · ExAero 52/54 · pick a bar, adjust spacers · bar-centre 460 / 609 · saddle tip → hoods 633 / 64
Retül targets (bar centre ✕, hood trough ◆, saddle tip ▮). The saddle is shared by every frame (assumed set to the Retül position, tip −69), so saddle-to-hoods differences come from the cockpit only.
Model: bar centre = head-tube top + (spacers + 20mm clamp offset) along the steerer, + stem vector at (90 − HTA + stem angle), + built-in rise straight up. Hood trough = bar centre + (bar reach + 29) forward, +13 up (calibrated so Retül 460/609 → 564/622 with a 75 reach bar). Saddle reference height 686 from BB (Retül drop 64 + hoods 622). Spear M 543/379/72.9°, Arden M 538/381/72.1°, Arden S 522/373/71.3°, ER:ONE S 521/381/71.0°, ER:ONE M 538/386/72.0° (front centre = wheelbase − 408). Tavelo clamp offset 18.2mm, others 20mm; stems fixed per bar choice.