It looks like everyone is talking about using the satin in quilts...so your fray check would be inside seams...
If you are making a little girls princess dress, and she will just pull it on over her t-shirt & jeans to play dress up, fray check is fine inside those seams, too.
However, if you are making any garment where the fray check on the inside seams would be worn next to the body, be aware that fray check is plastic, and will be scratchy next to the skin.
... Just so you know...