I didn't notice that it was unlimited forts until someone pointed it out a few pages ago. Not sure that's the best setting.
I agree with those that have spoken up about round limits. Not really sure how that will play out with a 6 person game. If the winner is clear by round 20, then fine. But I'm not sure this will be the case. Perhaps you should do round 1 at a 30 round limit but reserve the right to change it to 20 for subsequent rounds.
Finally, you should revise the scoring to make it more fair between people who are in 6 and 5 player groups. Right now the players that get assigned to 5 player groups are at a disadvantage. Total points awarded/Players should be equal in both groups. Unless, I'm not thinking of something that seems to be the fairest way of doing things.
What I would actually do if I was running this is just be sure you get enough players to divide evenly by 6. You don't seem to be having problems getting sign-ups, so you'll probably have some reserves.