The affine upper-bound conjecture for sequential cable width

Let $G$ be a graph, let $\mathrm{lrw}(G)$ denote its linear rank-width, and let $\mathrm{lsfw}(G)$ denote its sequential cable width. Affine upper-bound conjecture. For every graph $G$,

$$\mathrm{lsfw}(G)\le 2\,\mathrm{lrw}(G)+2.$$

The preceding results establish the corresponding lower bound and settle the level-one case, while the upper bound remains open beyond level one. The conjecture proposes an affine calibration between sequential cable width and linear rank-width.