ethylene and the banana peel trick has shown some improvement in the chances people have of getting fem seeds, but obviously like most things pertaining to weed its not proven. their is an interesting thread over at grasscity that discusses this exact topic. i really dont want to advertise another site, but it is a very valuable thread with good info. originally the poster set out to see if the product "reverse" would actually reverse hermi's back into being only fem. basically he did a shit ton of experimentation and legwork, along with a few other growers and its some pretty interesting info. in his first test he got a 100% fem rate from it... he also looks into making your own type of product at home ("reverse" is expensive, and not worth it) anyhow i dont think i need to regurgitate all the info on here but i really do suggest you try and find it. if i can locate it ill come and give you a link or pm you with it if you want.