Really simple way to fix them
have in memory the memory the number of maximum PHs
say Notorious Monster[6]
and then have something that is based on a random number generator and do % 6 for the first pop after window
and when that pops the new storage is [5] or what ever number popped... until you're at [0] remaining or hit the NM the issue is since would have to in and change the code for every NM i doubt this would be implemented we can dream though~