Eliza Parker Sizing

I'm really interested in a final sale piece from Eliza Parker. In your experience is the size chart accurate?

I am 46 bust, 50 hip. I typically fall into the 18/20 range in many places but according to their size chart I would need 14/16. It recommends for this dress to go by bust measurements because it's a wrap dress. My bust and hips both fall in their 14/16.