A cubic centering-gap coefficient above one for symmetric decagons

A second-order shortening at a corner gives a family of origin-symmetric decagons near the affine-regular hexagon. For sufficiently small positive parameters in the stated regimes, the linear Banach–Mazur distance is determined exactly and all optimal sandwich maps are classified. Conditional on the specified hexagon results and localized orientation bounds, the unrestricted and centered vertex-index minima reduce to separate scalar minimizations. Their comparison along an explicit threshold path gives an intrinsic cubic lower bound of (11√2+4)/16, which exceeds one. The results are provisional.