The amount of strength needed can vary based on the other Loras used but generally it needs 1.0 or higher to appear correct. Usually I found around 1.5 to be best, higher strength can also make it more likely for eyes/nose/mouth markings to show up on the underwear, which you may like, but if you don't you can try adding "covered eyes" which may get rid of them. Of course, you should make sure to get rid of any prompts that "conflict" with the wedgie like eye color, face accessories, ties, etc. anything that's on the front of the character or else it might awkwardly phase in front.
