  We employ hydrodynamic simulations to study the effects of high shock
compression ratios, as expected for fast shocks with efficient particle
acceleration, on the convective instability of driven waves in supernova
remnants. We find that the instability itself does not depend significantly on
the compression ratio, but because the width of the interaction region between
the forward and reverse shocks can shrink significantly with increasing shock
compression, we find that convective instabilities can reach all the way to the
forward shock front if compression ratios are high enough.
