I'm working on a teen pregnancy body that's a modified version of the sun dress. It's upskirt and there's a deep split on the sides where the leg shows through (see the pic). I'n trying to figure out the best way to handle the UV map, but everything I come up with results in the top getting scaled really small. My problem is the overlap -- It's bad enough without the slits on the sides, but once they're added there isn't much room left for the nightshirt. the pic also shows side-by-side placement of the top and leg UV map positions to illustrate just how much overlap there is. Is there a good solution for this or do I have to deal with all the textures looking really big?

You could take a look at the mapping for EA's semi-layered clothing like the Master Suite long nightgown or the Supernatural slit-skirt dress. From my very quick look, they seem to be splitting the top and bottom at the waist and mapping the skirt parts on the sides next to the legs. I haven't looked at how much distortion this causes with a pattern instead of a solid color.

Unfortunate EA decided to use one uvmap for all the clothing(shoe, tops, bottoms and fullbody.
This means there is hardly any room on the map for clothing like this.
The alpha upskirtbottom i once did had the skirtlayer mapped on the right side but even then i had to scale it down(result was a bit blurry texture.)
http://www.modthesims.info/showthread.php?t=411123
I presonal would not map the topparts on the bottom area(wich is on the right of the legs)
Reason is that it will clash with bottoms that have extra parts mapped in that area.
The left side in the bottom area is used by tops so thats were you can map extra parts.

Thanks. I was afraid you were gonna tell me something like this. There doesn't seem to be a good option here. If I understand what you're saying Bloom, I can use both sides of the map for this mesh since it's a full body. There won't be any bottom parts used with it. I'll play around with splitting it into pieces and moving it around some. I don't have those EP's Cmar -- but I think I understand what you're saying to do. I've got some textures I made specifically for this top, and they wrap around the body across seams. Oughta be real fun trying to line everything up from side to side AND top to bottom if splitting it actually helps. They're classic cartoon characters so it'll have to be right, down to the pixel. I gotta start picking easier projects.

yes, if it is a fullbody you can use both sides

One more quick question about this and I think I'll be good. If I do this as a teen full body, There won't be any issues with the how a pregnant teen looks while wearing it, will there? Until there's more conformity with the teen pregnant morph, I don't think I'm the person best suited to start making teen pregnant separates. Waist mismatches drives me nuts!
This mesh got split onto both sides of the UV map if anyone's interested. I still had to scale it down more than I hoped to, but I think I can compensate by moving the planned textures up above the split at the waist. When life gives ya lemons -- add vodka.

i dont expect any problems

I've run into another new problem. The slit up the side of the leg was created by unwelding vertices and moving them apart. Now that I'm trying to fine-tune the UV map, I've noticed that the vertices on opposite sides of the slit are still mapped to a single UV point. Is there any way to split them apart? With the map looking like it does right now, patterned textures won't be an option.

strange, unwelding usually split the uvcoordinates aswell.(or did you choose unweld radial?)
If you can not manage by unwelding the vertice then select the faces of one side and temperary regroup that meshpart, that will split them up.
That does mean it will mess up the relation with the morphs, you have to make the same edit to those aswell.

Another option is to use the modelcleaner but i would be carefull with that.

I used unweld radial when I first started this mesh. I removed some faces at the same time and that was an easy way to do it. Regrouping the parts worked great -- the map is fixed. As far as the model cleaner goes, I use it very rarely because I don't know everything it does. Thanks!

the model cleaner will automaticly split up all vertice that are welded.
It does not split each vertex but uses the uvmap as reference, so a vertice with diffrent uvcoordinates will be split.