Hi Tom! By chance do you know some articles that describe the non-perfect rotation problem? I am trying to understand a little bit more the peak at 0 on the Q component, but I can not find any literature.
I look for the publications from Schneider by it does not mention anything about it 
Hey,
I guess this is an often dealt with (or ignored) problem, but well hidden inside articles.
I checked Felix’s dissertation here. Chapter 4.2 and appendix A have some insights. At the end of the chapter he cites work by other authors (Saul et al., 2000; Svenningsen and Jacobsen, 2007). Perhaps you can find more guidance in these articles.
I think the point of the above references is that if you really want to really separate the energies arriving at P and SV times, you need more than just a plain rotation. One interesting application is to deterimine near-surface S wave velocity.