How much does a stay sail really add?

[csandys]

That picture shows the yankee up, not the 135.

I wish I had it up the other day. We were casually sailing around Lake Union, but the fireworks barge takes up the center, leaving two slots to sail. Since it self tacks, it would have been nice to have when beating into the wind and not dealing with the genny on each tack.

I'm thinking of making it optional, but I need to work out boom storage and a way to keep the stay happy when not attached.