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Let $C=S/(8\pi \mu )$. The image of the other stresslet is at relative vector $(\ell ,0,-2h)$, for which $r^2={\ell }^2+4h^2$. Summing direct and image interactions gives the free-surface interaction of two parallel stressletsThe direct neighbour gives no vertical velocity. Its image gives a vertical correction of order $Ch/{\ell }^3$, compared with the own-image attraction of order $C/h^2$. Thus for $h/\ell \ll 1$,The height evolution is unchanged to leading order, while the repulsion is twice the unbounded-fluid value: the neighbouring image lies almost at the same horizontal separation as the real neighbour. At this order ${\ell }^3={\ell }_0^3+3St/(\pi \mu )$ and the height follows part (c). The equality for height is asymptotic, not exact; weak neighbour-induced orientation changes are also neglected in the stated parallel configuration.