Absolute stability region
Stable region in red.

Coefficients

\begin{align} \begin{array}{c|cccccccccc} & & & & & & & & & & \\ \frac{1}{3} & \frac{1}{3} & & & & & & & & & \\ \frac{2}{3} & \frac{1}{3} & \frac{1}{3} & & & & & & & & \\ 1 & \frac{1}{3} & \frac{1}{3} & \frac{1}{3} & & & & & & & \\ \frac{1}{3} & \frac{1}{8} & \frac{19}{72} & - \frac{5}{72} & \frac{1}{72} & & & & & & \\ \frac{2}{3} & \frac{1}{9} & \frac{4}{9} & \frac{1}{9} & & & & & & & \\ 1 & \frac{1}{8} & \frac{3}{8} & \frac{3}{8} & \frac{1}{8} & & & & & & \\ \frac{1}{3} & \frac{1}{8} & & & & \frac{19}{72} & - \frac{5}{72} & \frac{1}{72} & & & \\ \frac{2}{3} & \frac{1}{9} & & & & \frac{4}{9} & \frac{1}{9} & & & & \\ 1 & \frac{1}{8} & & & & \frac{3}{8} & \frac{3}{8} & \frac{1}{8} & & & \\ \hline & \frac{1}{8} & & & & & & & \frac{3}{8} & \frac{3}{8} & \frac{1}{8}\\ & \frac{1}{8} & & & & \frac{3}{8} & \frac{3}{8} & \frac{1}{8} & & & \end{array}\end{align}

Properties