Prom Dress Help!!!

I am 17 and my prom is coming up in 3 months. I have started to make my prom dress!!!    I made my own pattern!!! (I am VERY proud of myself because that is the first pattern I ever made!  )  Here are some questions I would like to get answers too and here is pictures of the inspiration of my dress: http://www.lindsayfleming.com/clara/clara.html

1.  I am making the top out of a jersey knit (Really soft and breathable!)  My worry is that the under arm of the top will stretch because the bottom will be a little heavier  .  How do I keep it from stretching?  I don't want to use binding becuase it may look funny...  any ideas? 

2.  The bottom of the dress is going to be A) A silk full circle skirt with a slit or B) a silk tulle handkerchief skirt.  Either way I want it to have lots of movement!  My question here is what type of hem to use.  I was thinking about a overlock seam, but I have never done one of those before.  How difficult is it and what other hems could I use? 

3.  Color.  I have not bought fabric yet and I am unsure of what color I want.  I don't really want white and I am looking at shades of blue.  Maybe a navy?  Any ideas? 

Thank you for your time!!!     

1. Could you stick a stabilizing tape in the hem? This might keep it from stretching too much.

2. I would use a rolled hem for the skirt. It would be the easiest and fastest for this type of garment.

3. Navy sounds great. What about a deep purple or an ice blue?

I never thought about ice blue!  That would look really nice!  I will look for some of that stabilizing hem tape!  My book has a tutorial on a rolled hem line as well!  Thank you so much!!!