Owlvamp, thank you for hosting these! I know it's a lot of work.
I would say I prefer to have 21 swappers before the swap begins. Someone said previously that we knew we had fewer swappers this time, but I don't feel like I can say at the last minute, "Never mind. There aren't enough swappers so I'm not sending in my squares."
I never minded receiving doubles as an inevitable part of swapping, but to tell the truth, I do the swaps intending to get more unique squares, not bunches of doubles to give away.
Is there some way to make the deadline float, depending on how many swappers there are? ("Open to the first 25 swappers"?)