lining a kilt is one thing. Stitching in multiple layers...that's something else and seems doable.

Gluing two layers together, especially if you try to glue really large pieces of cloth together....no, for the reasons that the Wizard pointed out. It will be rigid as a board, yuck. Besides, the $$$ you will spend of all that glue-web stuff more than makes up for the extra cost of the different fabric.

Do you HAVE to have EXACTLY 12 ounce material? How about 10 ounce? How about 13? It's out there.

Of course, if you just GOTTA do this, then forge ahead and let us know how it goes.