I've done patternmaking for brides who wanted to save money by getting a store bought pattern and I went to the butteric website and the closest I found was B6533. It is an a-line full length dress with princess lines and is fitted and strapless. What you could do is maybe just to be on the safe side, make the skirt wider to start. What they have done( David's Bridal) is they have pulled up the outside skirt along the seamline and stitched it to the underlining to create this effect. Make your muslin from a fabric similar to what you want it made out of . Good Luck
