the one possible disadvantage of adding RGB to luminance is that, if you have short RGB exposures, you could possibly end up with slightly
lower SNR because the read noise you introduce from the RGB subs overwhelms the slight reduction in shot noise from the extra signal in those subs - if you are going to add in RGB subs, the exposures should be roughly 2-3x as long as the lum subs for best effect. Probably always worth a try though if using PI
- it does a good job of getting the best possible stack results, even if the exposures are not optimum.