It doesn't feel like things are going to fall out. My stuff usually fits halfway, so it's not overstuffed. The medium size fits a good amount of stuff. That Amazon organizer is nice with the zipper to extra secure your stuff. I use it all the time now.
No, it doesn't fill heavy while wearing it. I have it about half full. Might be a little heavier if I had completely full and depending what I put in it. Overall, I would not say it feels heavy
