Well, common sense must rule on this one. Yes, everyone needs to wait for most of their teammates to get to the crate before opening it. However, there are times where I'm waiting and most of my team is there and I can tell they're also waiting for that one last teammate to come in and open the crate. And he's really close and all and yay we're all gonna get heavy. Then a member from the opposite team noticed were camping at our crate, loads his rocket launcher from like 10 miles away and wipes us all. And now they can get the second crate too. You won't even see them in your radar. Heck, I usually do that if I get the chance. So as a personal rule, I wait about 5 seconds after the other team opened their heavy crate, just for safe measure. After that, I'll try my best to wait longer than that but it's also fair game.