Finish all layers about 1/2"longer than your finished length. I make the lining 1/2" shorter than the face fabric, and the interlining 1" shorter than the face fabric. I then serge all layers together at the top and pleat them all together. I usuallly make mine 2 1/2 times the fullness so it does not gather well by the method you suggest. I generally use the side of the point of my seam ripper to make 1/4" tucks and push them under the foot. Use 1/2" seam allowance to sew to the decking. You want all layers to act as one to give a great weighty hand.
Hope this helps...

How full a gather do you want? How 'heavy' is the fabric you're using. If it's heavy, like denim, I'd probably gather just the 'denim' and not the other layers. If it's like a swiss dot I'd gather all three together.

I don't like 'one step' work, I still do everything in stages. I would sew the layers together at the upper edge and then I would gather or pleat. With that much fabric I'd zig-zag over string. That way I can pull the string anywhere along the yards of gathering for easy adjustment. Then I'd baste the gathers before attaching to that part that goes between the spring & mattress.

Dirty Knees,
I'm curious,where did you get your board name??? Are you a gardener??? Nosy aren't i ???
Kathi

You want to gather them all together or your linings won't be full enough. If you want to gather at the machine, hold both sides of the fabric (either side in front of the needle) and make your gathers, a little at a time, and sew over the gathers as you go. And sew a little inside your seam allowance so the thread won't show. Holding your finger behind the needle is just going to bunch up your fabric.

Thanks for all of the suggestions. I'm sure I won't even have time to doing any sewing until after the holidays.

By the way, I am a gardenweb member and PepPep is short for my dog's name, Pepper. No children, so she's my baby!