I always use a stop bath and I've never had pinholes in any film. I don't use commercially bought stop bath though, just 10ml of glacial acetic acid to a litre of water. Perhaps the problem only occurs with higher developer temperatures; I've noticed quite a few posts on this forum talking about developer temperatures of 75 Farenheit and above. 68 degrees has always been the standard as long as I can remember, and I always develop at that temperature.(posted 8831 days ago)Potassium Metabisulphite at 10 grams to the litre would make a milder stop bath. It's the chemical most commonly used to acidify fixing baths, so it shouldn't give any problem.