If my bad english have made me read right, you've problems with scaling the clothes to the new dimensions of the character. I never had problems doing it, just scale the character's body, conform the dress, go to the dress body and apply the same scaling of the character. If you scaled different parts of the character, for example the abdomen, do the same with the dress...
About how the dress "works" on the character, for example the way it bends when you pose the character, I've seen only few dresses that bends correctly, not only for Posettes but even for the newest characters and packages. This is because the dress maker can't copy the "technology" for copyright reason, or the way the character bends their part so you will see for sure the dress not bending perfectly. So you can find a perfect dress for
Posette, but it's more difficult to find a perfect dress for a commercial character. This is why I tend to use the dynamic dress method, sometimes a dress born to be conformed doesn't fit well, but I transform it in an object and use it as a dynamic dress, at least for the final pose...
