Mercerized Cotton Options

I've got in my stash almost 2,000 metres of Schoeller Esslinger yarn
called Palma, which is 100% cotton, mercerized and singed (whatever
that means). It's about a sport weight and is nice and satiny.

It's similar to Patons Grace, and I'm told that it'll work up
approximately the same way.

Now, since I've got enough for a sweater for myself (and then some, I
think), I'm wondering if it's truly a good option for a sweater. Does
this type of cotton end up stretching and sagging? The saleslady at
the yarn/craft store used it for a tank top, but she used it doubled,
and it was stretchy and saggy. This is NOT my style

So I'm turning to the RCTY experts: Will this type of yarn make a
sweater that will keep it's shape? Or should I make a wrap or
something similar out of it? I was hoping to make a sweater for work,
since it works up so beautifully and is wonderfully satiny soft (I've
used it for a scarf for my DD and it seems to stretch quite willingly),
but a wrap or stole would probably work well, too.

I was thinking that keeping the sleeves above the elbow would eliminate
elbow sagging, and that wrap styling would perhaps eliminate
waist/hipline sagging. Perhaps? But what I was really hoping to make
was this baseball-shirt style with the sleeves shortened to 3/4 length
and some waist definition added:
http://knitty.com/ISSUEsummer05/PATTbaseball.html

Thanks for anything you all can offer!!

Michelle