What kind of fabric is it made of, and what do you mean by underlining? If you're talking about basically lining the dress twice, I would think it would depend only on how shear the top layer is. With girls not wearing slips much anymore, you want to be sure the guests aren't distracted by see-through bridesmaid dresses! So, if the top layer and its lining do not block enough light, you may need another lining. Otherwise, if the top layer isn't super thin, one lining would be enough. Too many layers can just make a heavy dress.
Also, I think I remember this from home ec.: with parts of the dress being bias cut, you can cut the lining with the grain, and that should stablilize the bias layer. Hope this helps--If someone else out there knows more, please jump in. Cela
