After all your wonderful suggestions, I did end up choosing Ladies 1931 Dress from Vintage Pattern Lending Library for my Gatsby Dress.  I just can't seem to get enough of those VPLL patterns!  More on THAT later.  Here is the story of how I came to use a Vintage 1940's dress for my "muslin" prototype.

On Instagram I follow of @MakeThisLook, @ShopMakeThisLook & @SewWeekly which are run by a darling woman, Mena Lazar, who sews her own vintage clothing & sells vintage fabric (go figure?). On @SewWeekly, she has a sewing challenge going on for the month of August and has one sewing challenge per week.  If you don't know about these Instagram Challenges, they are fun ways to connect with other like-minded or like-crafted people and also a forum to show off your work. 

Because the Summer is so busy, I can never really do much with these challenges but I was prodded into participation with an event looming on the horizon - Gatsby Summer Afternoon.  I was inspired to participate in the #SewWeeklyLivingDangerously challenge which prompts participants to sew with a prized fabric that they've been hoarding.  Well, I kinda changed that a little and decided to "Live Dangerously" by using a dress that was gifted to me, for the prototype fabric.  "Why is this dangerous?" you ask. 

#1 - you don't know how much fabric you REALLY have until you take it apart

#2 - Cutting into an existing and also vintage dress is very RISKY.

Why did I use this dress?  I liked the fabric, but not the dress.  It's a 1940's Rayon Satin Dress in two colors - Black and Peach.  The fit was all wrong and, there was a lot of fabric.

So, after disassembling the dress, I soaked and washed the peach colored fabric in Oxyclean.  It was stained badly.  Not good if I was actually able to wear this new dress. The black fabric was in relatively good shape, so I did not soak or wash it.  Amazingly the washed fabric came out beautiful.  It was pressed and then squeezed to fit every pattern piece I could - mid section and top of skirt along with belt and bow & the sleeve ruffleThe black fabric was used for the remainder of the garment. 

Because I am rather short (only 5' 3 3/4" on a good day) I knew the dress had to be shortened AND I had to squeeze what I could out of the fabric.  In order to make the pattern and fabric work together, I had to shorten all the bodice pieces as well as the skirt pieces, in what added up to about 6" overall (3" on the lower skirt, 1" on the bodice and 2ish" on the upper skirt).  All the pieces had to be seamed/pieced with the exception of the back bodice,sleeves, midriff and upper skirt pieces.

I also did some minor fit work on the bodice by picking up the neckline at the front shoulder.  Otherwise, nothing.  And, I do really like this dress.  For the actual Gatsby dress, I will add a little bit to the low hip (it's a teensy bit snug) and use the sleeve from another VPLL dress (Pattern 3221 Dress with front bow) that I used for making my 1930's skirt inspired by Miss Fisher.  I used this sleeve for another dress (pictured below).

That's it for now.  Until next time, Happy Sewing!