\makeatletter
\begin{lrbox}\shippingAddressBox
\parbox{\useplength{toaddrwidth}}{
\backaddr@format{\scriptsize\usekomafont{backaddress}%
\makeatletter
\begin{lrbox}\shippingAddressBox
\parbox{\useplength{toaddrwidth}}{
\backaddr@format{\scriptsize\usekomafont{backaddress}%