  We perform fully dynamical simulations at small quark masses by reweighting
in the quark mass, calculating the weight factors stochastically. This approach
avoids some of the technical difficulties associated with direct simulations.
We find that the weight factors fluctuate only moderately on nHYP smeared
dynamical Wilson-clover ensembles, and demonstrate that the overlap between the
original and reweighted configurations is large both for short and long
distance observables. We could successfully reweight 16^4, (1.85fm)^4 volume
configurations from m_q 20 MeV to m_q~5 MeV, and 24^4, (2.77fm)^4
configurations from m_q~8MeV to m_q~MeV quark masses, reaching the
epsilon-regime. Using the pseudoscalar and axialvector correlators we predict
the low energy constants Sigma and F and study their volume and mass
dependence.
