Disc instability models, evaporation and radius variations

We show that the outcome of disc instability models is strongly influenced by boundary conditions such as the position of the inner and outer disc edges. We discuss other sources of uncertainties, such as the tidal torque, and we conclude that disc illumination, disk size variations and a proper prescription for the tidal torque must be included in models if one wishes to extract meaningful physical information on e.g. viscosity from the comparison of predicted and observed lightcurves.