  We find unconventional Mott insulators in a quasi-2D version of the
Shastry-Sutherland model in a magnetic field. In our realization on a 4-leg
tube geometry, these are stabilized by correlated hopping of localized magnetic
excitations. Using perturbative continuous unitary transformations (pCUTs, plus
classical approximation or exact diagonalization) and the density matrix
renormalisation group method (DMRG), we identify prominent magnetization
plateaus at magnetizations M=1/8, M=3/16, M=1/4, and M=1/2. While the plateau
at M=1/4 can be understood in a semi-classical fashion in terms of diagonal
stripes, the plateau at M=1/8 displays highly entangled wheels in the
transverse direction of the tube. Finally, the M=3/16 plateau is most likely to
be viewed as a classical 1/8 structure on which additional triplets are fully
delocalized around the tube. The classical approximation of the effective model
fails to describe all these plateau structures which benefit from correlated
hopping. We relate our findings to the full 2D system, which is the underlying
model for the frustrated quantum magnet SrCu(BO_3)_2.
