I was raised Mormon, and I don't ever recall being told to wear two pairs of pants. As a matter of fact, although pants and long shorts were condoned, you were really looked upon favorably for wearing dresses like a good girl.
The shoulders thing, though, is real. We moved to Florida from Colorado when I was seven, and everyone else was running around wearing short-shorts, tanks and short hair on account of the brutal summers. There we were sweating in long pants or short to our knees, short sleeves, and hair down to our waists, and practically fainting from heat exhaustion. And my mother can't figure out why I still resent that. Matter of fact, she still disapproves when she sees me wearing a tank-top, because it's so immodest and against god's commandments. (snort)