I still have a few days left before the deadline. I was told that the deposit is to hold down the group price. If I dont have enough rooms then I loose the deposit. If I need more room than the originally booked, then they can't guarantee the price but they will be part of your group still. I dont pay for any other costs for the reservation. I hope this helps. Congrats and good luck. Keep me posted. Do you have a TA?