  We show that the critical fields of the magnetization plateaus of the
Shastry-Sutherland model decrease significantly upon increasing the ratio of
inter- to intra-dimer coupling, and accordingly that the magnetization plateaus
of SrCu_2(BO_3)_2 shift to lower field under pressure, making the first two
plateaus at 1/8 and 2/15 potentially accessible to neutron scattering
experiments. These conclusions are based on the derivation of an effective
classical model of interacting pinwheel-shaped spin-2 bound states using a
combination of perturbative and graph-based continuous unitary transformations,
showing that pinwheel crystals are indeed the lowest-energy plateau structures
at low magnetization, and that a simple model of intermediate-range two-body
repulsion between pinwheels is able to account quantitatively for the plateau
sequence.
