Males are quicker to declare sex than females (usually), so the ones that haven't said a word are probably girls. You can increase your chance of females with ethylene gas. Its easy to do this old school. Just place bowls of ripening fruit around. Bananas & peaches ripen fast & therfore put out a higher concentration of ethelene than say apples. Keep an eye peeled for those damned little fruit flys! Put pest strips (hanging) in your grow space, if they still make them. I do this the same time I put them in 12/12. The youngens with their high tech ways would have you going to great expenses with filled tanks of manufactured gas & emitters, but not necessary. Your biggest expense my way might be eliminating fruit flys. I've never had the need to try & 'turn' males to females, but it might be worth the try since you have so many males.
You could let your fastest male mature, then collect & save the pollen in something small, like a 35mm film canister or sm baby food jar & store in the freezer. Unless one of the guys have an idea what to do with them, I personally would turn them into compost. You could dry & smoke the leaves & get somewhat of a buzz, but I can't stand the taste. Up to & your guy.
Peace!

P.S. you can use your neem oil on those pesky little fruit flys. Prevention & cure! ;-)