Help with Simplicity 2250 - it's a sewing emergency!

Once upon a time there was a girl called Jorth. In her pattern stash Jorth had a pattern - Simplicity 2250 - and spent many a month waiting for the perfect fabric for the dress to come along.

Then one day she found it! She bought the required yardage, went home and cut out her pattern and then watched with dismay as the weather got cooler and cooler. She decided that she would wait until next summer to make the dress, and put it away and began to work on her winter projects instead.

The seasons rolled past, as they always do, and one fine spring day when Jorth was tidying up her sewing bureau she found the dress again - all cut out and ready to go. With delight she unpacked her sewing machine, set her tools out on the table next to her, and began to sew. Days passed and Jorth was up to the bit where she needed to insert the elastic in the back casing.

But horror! Could the elastic guide be found? Alas, it could not, though Jorth searched high and low. "Noooooooo!" she moaned. "Don't let the dress remain unfinished forever due to my slapdash packing away methods!"

So close, yet so far!

So fellow bloggers, seamstresses and friends: can ye help? I can't believe I have navigated the minefield of the bodice darts, heroically tackled the pleated and gathered skirt, even managed to decide between wide straps and thin, but have fallen at the elastic casing! If anybody has the Simplicity 2250 pattern at home, I would be forever in your debt if you could let me know how much elastic is required for the size 8 back elastic casing.

Just think of the amazing sewing karma you'll get yourself! The sewing gods will be preparing a special place in sewing heaven just for you, and using their special magic to make sure you never have trouble putting a zip in again! I promise!