On the other hand, a regular mastercoin send only takes about 30-35 bytes. Maybe Counterparty could consider selectively sending common, small transactions with OP_RETURN, and using multi-sig only for relatively unusual transaction types?

By the way, thanks both to my mysterious benefactor and to whoever thinks I'm Satoshi. I'm not sure my previous comment merits either of those compliments, but I appreciate them. My SX stealth address is SghSgpVgk7yAFx91DxwfE84Dm6r2hwSpMWcFJbR9wQTAv7pgq61Nx3dNsn if anyone is interested - and if they are, I'm sure they can send me a nonce without too much trouble