on the halter top: i had a problem with gapping on a racer back swimsuit i made that was cut wrong, and had to use constrained groups (which i tend to avoid) to keep it from gapping in certain poses, despite the tight fit and friction. it was OK, but it was still  (very) wrong in shape, so i started to look for more references and information about how to actually sew one.  i immediately encountered information about how to cut a swimsuit so it didn't gap.

apparently, anything that hugs the body at an angle like that has to be dealt with carefully in real life. this is what i meant by aspects that might appear to be bugs but in reality are just cloth behaving like cloth.  there's a reason some clothing designs fit well, and some sag and gap in unattractive ways. and  why some fit very well and some require double-sided tape or constant tugging to keep in place (see Star Trek). 

making dynamic clothes is as much like making real clothes as the simulator can make it.  cut and fit are very important.  that said, i'd still like a tension setting so it wouldn't be necessary to scale up figures to create tight clothes.  if we could just say the initial state had a certain tightness, it would be much better.

oh, and just to make another point about topology- LaurieA's dress is a good example of how you can use it to your advantage.  so far we've been addressing tris vs. quads and subdivisions as whole mesh transformations.  as a result, her dress has the highest poly density where it doesn't need it  and the lowest density where it does need it, like at the bottom of the skirt.  the differential in the original wasn't a big deal (imho), but as the whole thing was subdivided, the top and upper arms became very resource heavy while the bottom of the dress just reached medium high (imho) resolution.

i'm not exactly sure of the solutions, and i'm sure what you would do would depend on how much structure you want to add to your piece, but getting your resolution highest where you need it most seems pretty important.

oh!  and i don't think it changes anything to scale the outfit during the sim.  i'm pretty sure if it's 100% at the start, it simulates as if it's 100%.  i tried scaling the swimsuit down (by a lot), and it had no effect at all.  not that this is what TrekkieGrrrl did, her comment about scaling just brought it to mind.