I don’t have a problem with ammonia odors in my stalls. I put in a layer of 3/4" drainage rock first followed by a layer of 3/8" crushed clean, for a total of about 6"-7" inches under the Stall Savers. I’m using pelleted bedding and usually sprinkle Sweet PDZ on the pee spots once a week.
My horses are free to come and go out of their stalls and I have a shed row-type barn. I hose out and wash the stalls a few times a year.
All of my stalls now have Stall Savers and I still love them 4 years later.