In my experience the biggest problem with large groups us the amount of time it takes for combat rounds. Compound that with people being distracted while online, and I think 6 players will be a bit much. If you have everyone prep their turn, and streamline the enemies' turns, it might be ok.
wow great point. with more players combat would have to be more difficult as well. i also tend to run high magic games and with magic items, six players and a ton of mobs it could drag in combat