LDM-151 coverage of wavelength-dependent PSF models is spotty; my quote from a recent dm-sst email:
The fact that the full-visit PSF model is wavelength dependent is mentioned in LDM-151 5.1.1 (under FitPSF) and 7.19. It should be discussed much more prominently in 7.11.3; that's my mistake. The plan to put DCR in the PSF, not the WCS, is mentioned in 6.13.3.
We should make sure our approach is clear from reading any of these sections (possibly by referring to other sections).