Good luck to you with sailing your yawl. You may wish to play around with a mizzen staysail since it is considered a great asset to the yawl and ketch rigs. It is an easy to manage sail and a great puller. Functionally--the mizzen staysail is hoisted to the mizzen masthead and tacked down on the weather side-deck. The sheet is usually led through a turning block on the mizzen boom and belayed near its goose neck. If you don't have running backstays, it is very easy to have and use the mizzen staysail. With running backstays, you have to be a bit more careful and clever. Some owners of yawls use the mizzen staysail without even using the mizzen sail because it is the staysail that is so useful!
Answering many questions you may have about the yawl rig, there is a great chapter on the history and development of the yawl in John Leather's book "The Gaff Rig Handbook". (this book is available from Amazon.com as well as other marine-focused booksellers like seabreezenauticalbooks.com)
Quoting from this resource:
"The yawl rig evolved for convenience of handling by docking the long boom of a cutter and adding a small mizzen stepped on the counter or transom of the vessel. For many years the definition of difference between a yawl and a ketch as been the yawl's mizzen steps aft ot he rudder stock and the ketch's forward of it. However the rig should more practically be defined by the relative size of the mainsail and mizzen rather than the position of the latter.
The date of origin of "yawl" applied to rig is obscure but appears to originate in the early 19th century, probably contemporary with the many coasting and fishing craft setting the dandy rig, where were in effect short-boomed cutters with small lug mizzen stepped aft and usually sheered to an outrigger. The early Clyde yacht Lamlash, built by the first William Fife in 1814, was so rigged...."
further of interest the author tells us:
"The shape of yawls' mizzens has changed over the years. Working craft favoured the standing lug, with or without a boom and sheeted to a bumpkin. This fashion persisted in early-19th century yachts until gaff mizzens became popular in the 1880s. A bermudian or triangular mizzen is probably the smartest setting, most efficient and lightest sail, which suffers least from the mainsail’s backwind but may require a very tall mast, making staying awkward. It is popular belief that a yawl’s mizzen is only a steering sail to make her “look up into the wind”. In a yacht designed for the rig it should be considered a driving sail otherwise it is worthless.
Old boats are sometimes converted to yawl rig in an attempt to improve their steering and some have even had the mizzen boom sheeted to the rudder in attempts to make them quicker in stays, with little effect.”
Finally, this chapter has several pages describing particular yawls, working boats and racing yachts alike. He does state that:
“the big racing yawls died out in the 1880’s but revived strongly after 1896 when rating changes caused the splendid larg cutters…to dock their main booms and step a mizzen in order to win. The mainsail was much to large in proportion to the mizzen, which was almost useless on the wind causing it to be despised by yacht skippers and crews as being ‘only fit to cheat the rule or fly the ensign from’”.
“Joshua Slocum converted his sloop Spray to a yawl after sailing across the Atlantic, down to South America, and through the Straits of Magellan, by stepping a standing lug on her transom, sheeted to a bumpkin. It reduced the size of her mainsail and improved her steering, on the wind, but he furled the mizzen when running.”
Again, good luck with your yawl.