Summarizing the results of the iodine-labeling experiments, the electron density difference data from synchrotron experiments and in-house data are not in agreement. While the synchrotron experiment faced technical challenges related to the relative low photon energy (L III edge) and sample realignment after beam drift when changing the energy, as well as intrinsically lower contrast, the comparison of two different, not necessarily isomorphic, samples in the in-house study may also pose a challenge. In other words, the differences from one sample to the next may be on the same order as the label effect itself. Note that one needs a much higher reproducibility to interpret the difference curve than the rather gross features of the profiles before subtraction. Therefore, we consider the results regarding the membrane repeat spacing to be more reliable and consistent than conclusions drawn from the peptide labels.