Measurements of the fusion of ${}^{16}\mathrm{O}$ and ${}^{27}\mathrm{Al}$ with a series of germanium isotopes are analyzed within a coupled-channels approach. It is found that couplings based interactions that are linear in the deformation amplitudes are insufficient in reproducing the data. In order to obtain reasonable fits, it is necessary also to include couplings based on quadratic interactions. The analysis suggests that the nuclear radius of ${}^{72}\mathrm{Ge}$ is significantly smaller than predicted from a smooth interpolation between other germanium isotopes. The large prolate deformation of ${}^{74}\mathrm{Ge},$ which has been proposed as the preferred solution to measurements of the quadrupole moment of the ${2}^{+}$ state, is not supported by the analysis; the near spherical solution is more likely.