SaintFox,

That's a nice render.
If you want to use a strapless you could try setting the top edge of it as a constrained group for the cloth simulation. Over in the Antonia conforming clothing thread I described how I made and used a constrained group to stop my shorts falling down when i clothified them. As with many things I'm still learning and trying things out, but the method worked for me.

Cheers

Ian