Well a darth suit will fill out your frame a bit, but seriously unless you are 6'7" and have a bodybuilders frame.david is out.
I also would tell you that vader suits are freakin hot, and latex under it? You will die of heatstroke.
I have a supreme helmet, and a standard chest peice.same problem...I just trimmed the bottom of the mask.
For it to fit properly, you really need the rubies chest armor, which is on e-bay sometimes.
But if you really want a latex chest here ya go...good site.
http://www.xtremedesignfx.com/