I didn't have the dress custom made because I'm particular and prefer to go to my tailor for that sort of thing. So I can't attest to the custom sizing. In that same vein, I ordered a size up - an 8 - with these measurements: 34, 28, 39. The 8 was huge and definitely had to be taken in all around.
Moving on, I can tell you this dress is incredibly well made. The lining was great - seriously you won't have problems there. And the placement of the seams along the bust and torso hugged my body shape and me feel confident, secure, and sexy. The visibility of the illusion necklace changes depending on the lighting. It's visible enough to add a smidge of sexiness to the garment, but not too see through to not be able to wear a normal bra with the dress if you wanted to.