Young's modulus of 1.5 MPa and Poisson's ratio of 0.5, one would expect a 20 nm probe and 2 nN indentation force to produce aFF of around 50 nm. In contrast to these examples, Brune, et al. reported a 30 nm interphase measurement in their rubber interface mimic under these conditions, i.e., well below (λ / aFF) = 3. As there was no plateau in stiffness or apparent modulus to quantify, we would not expect a reliable measurement with our approach. However, our work does not exclude the possibility that more elaborate modeling and parametric inference approaches such as the one undertaken in Brune, et al. could produce reliable measurements even at lower λ / aFF values.