Density-Matched Shift Profiles and Radial-Pressure Reduction in Positive-Energy Warp-Shell Metrics

A positive-energy warp shell carries an off-diagonal shift of amplitude β on a static matter shell. Reconstructed from the public implementation, the published construction satisfies the null, weak, strong and dominant energy conditions up to β = 0.0304. We derive the shell’s first-order momentum density in closed form, checked independently against the ADM momentum constraint, and show that a shift whose radial bending is matched to the shell density controls its second-derivative part exactly. An exact match fails in the low-density fringe at about 0.075, and a slight taper (q = 1.04) removes that limit. Together with zero background radial pressure and a heavier, thicker shell, the estimated first-loss threshold reaches 0.0896 for a reference design and 0.0953 for a thick design that keeps a 2 m flat core. Both values are reproduced on three grids with targeted probes. These are numerical thresholds under a stated protocol for a different static configuration from the published one, not continuum certificates. No matter model for the shifted spacetime is claimed.