Hi, I'm eelikay, and halo will be with me until the end. I sure in the near future I will be able to enjoy full lobby custom games on Halo 3, Reach and 4 like in the old days! It's just so hard nowadays to get full lobbies on your own!
Yes the more your active in the community the more people will join your lobbies. I had to join several lobbies before I came big. It's been a whole year from when POSL had announced that they were in business. Trust me just keep joining others and make you-self stand out and you will get full lobbies in no time.