  We report on our first experiences with a mixed action setup with overlap
valence quarks and non-perturbatively O(a) improved Wilson sea quarks. For the
latter we employ CLS Nf=2 configurations with light sea quark masses at small
lattice spacings. Exact chiral symmetry allows to consider very light valence
quarks and explore the matching to (partially quenched) Chiral Perturbation
Theory (ChPT) in a mixed epsilon/p-regime. We compute the topological
susceptibility and the low-lying spectrum of the massless Neuberger-Dirac
operator for three values of the sea quark mass, and compare the sea quark mass
dependence to NLO ChPT in the mixed regime. This provides two different
determinations of the chiral condensate, as well as information about some NLO
low-energy couplings. Our results allow to test the consistency of the
mixed-regime approach to ChPT, as well as of the mixed action framework.
