The coping middle level is (Level underside + step top)/2. P3's top and P6's upper limit are this level, and e_top is the
step top minus it (P1: 1322, replacing the 1623 reverse-engineered value). On P1 P3 goes from 38 to 39 ties and P6 stays at
8 levels. With taper h2 = 3000 the middle level is 13275: P3 37 ties, P6 8 levels (32 bars), e_top 2072.
Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>