  We discuss reflection factors for purely elastic scattering theories and
relate them to perturbations of specific conformal boundary conditions, using
recent results on exact off-critical g-functions. For the non-unitary cases, we
support our conjectures using a relationship with quantum group reductions of
the sine-Gordon model. Our results imply the existence of a variety of new
flows between conformal boundary conditions, some of them driven by
boundary-changing operators.
