I've started looking at PPS fields to see if I can glean any additional information about the "flux discrepancy" from them.  However, the results are, as usual, unenlightening. There is no consistent increase in flux when 3 PCA components are used instead of 13 PCA components - very plausibly an indication that 13 PCA is not too much to subtract because it's only atmosphere.  Similarly, there is no obvious benefit to using a quadratic sky estimator instead of a PCA estimator. I'm using aperture photometry (without background subtraction) on identical fields to perform these comparisons.  I've selected (arbitrarily) the l357pps source as my comparison source.  The next step (ongoing) is to compare to the co-added maps and crosshatched large-scale maps of the same field. (next step) PPS < single cross-hatched large-scale observation pair < 13PCA full combined map < 3PCA full combined map. Unfortunately, this result implies that the small maps under-recover flux, which suggests that the large maps are too bright, which is the opposite of what we expect.  Additionally, lower noise -> more flux recovered? When background subtraction is included, the 3PCA and 13PCA fluxes match nearly perfectly. Despite the failure of this test (PPS < full field), I will do a systematic comparison of PPS sources with 0PCA + masking to the large fields in the hopes that doing so can provide a legitimate estimate of the "scale factor" from treating small and large fields differently.