Frankly, we used a lighter weight sail I call a drifter on the mizzen rig rather than the standard cruising sail that is technically the mizzen stay. The reason we didn't like to use the standard mizzen was that it was a real pain to fold being rather large and stiff. The lighter sail we used could stuff into a bag. As a result, we never used the drifter in wind over 15 kts apparent but then with wind over 15 kts, I was quite happy to cruise along at 6-7 kts with just the jib,main, and mizzen.
What hasn't been mentioned in response to this inquiry in the forum is the fact that the mizzen stay tack must be anchored about three feet above the deck to clear the main sheet (and the dodger of course). When you have your mizzen stay sail made, the sailmaker can integrate this in the sail's internal stay or you can add it later with an extension -just make sure the sailmaker has the right dimension to begin with.