  We present the results of an investigation of a mixed action approach of
overlap valence and maximally twisted mass sea quarks. Employing a particular
matching condition on the pion mass, we analyze the continuum limit scaling of
the pion decay constant and the role of chiral zero modes of the overlap
operator in this process. We employ gauge field configurations generated by the
European Twisted Mass Collaboration with linear lattice size $L$ ranging from
1.3 to 1.9 fm. The continuum limit is taken at a fixed value of $L=1.3$ fm,
employing three values of the lattice spacing and two values of the pion mass
constructed from sea quarks only.
