Read moreEDIT: The below is incorrect.
So please correct me if I'm wrong.
Pen Type # of Animals (Current) # of Animals (Nerf) Regular #1 10 1 Regular #2 10 1 Breeding 10 2 Total 30 4 So despite it taking weeks/months to get some shinys currently. You want to make it 7.5 times longer to do (or 3.75 longer with the double shiny).
In your other post you mentioned dropping it to 3x instead, so I'll assume it's for both:
Pen Type # of Animals (Current) # of Animals (Nerf) Regular #1 30 5 Regular #2 30 5 Breeding 30 10 Total ...
These numbers are only assuming non-breeding pens. The breeding pen is double as fast to get the shinies, actually it's higher than this as the hereditary nature of traits has increased so it's easier still, so if you are hard farming shinies the breeding pen is (and always was) the best way to go. The normal pen breeding is a boost on top of the original feature.