Dear artiste6543, from here it looks as if the garment is very tight vertically, is adjusting the measurements of either avatar or pattern pieces an option?

If you want to achieve it via pinning, the pinned area should rather be where the wedgie occurs and then you can pull this portion down. It will however not be so easy to make it look smooth then.

If accurate fit is not your highest concern, it could also help to set the avatar's skin offset up so that the fabric cannot snatch in in between the thighs so much.