It really makes it more cost effective to send in more sets because of the postage. If you have access to other poly envelopes I am ok with you using one of those if only sending in one set. Just enclose one for return shipment. I have even received some squares in another swap and a taped heavy duty ziplock bag - I was surprised and thought it was rather funny. Upping the count is fine.
I have one more signee already - and hope all, Moonrise, are recovering from the flu. It has really been a tough season for it - I have tried to stay away from people as much as possible.