Instead of playing the stamp guessing game, go to your local post office and use the scales there. It will give you a definite postage amount to use.
What I do is...
1) Take both envelopes, the Playbill, and some 44 cent stamps to the post office. Also bring about $2
2) Weigh the Playbill in the return envelope, and place adequate postage. Put the Playbill, SASE, and whatever else in the send envelope.
3) (and I do this since it almost guarantees return of the Playbill) Take it to the customer service desk sealed, addressed, and ready to go. Have them weigh and code it, and you'll end up paying (in cash) the exact amount you will need to send it to NYC without wasting stamps.
Check out my eBay page for sales on Playbills!!
www.ebay.com/usr/missvirginiahamm