Success! Got it figured out. Believe it or not, it was because I had auto smooth turned on in Milkshape. Ugh. Such a simple solution that took days to find. I still don't know how to make morphs or how to make the dress work with sliders but the edges are fixed, at least.
I'm planning to write a tutorial but I'd like to at least figure out the morphs and slider issue first if I can.
I'm Lolabellesims. Hi! Check out my stuff at The Sims Resource and at
www.tumblr.com/lolabellesims. Maybe I'll go nuts and publish something here, too.