I think it will dry in a few days over the shell mold, but it will be very fragile so handle with care. I would dry it on the outside of the mold and when it is firmly set remove and slide it inside the mold so it dries on both sides and keeps it’s shape. Not sure how you plan to light it but am anxious to see the finished cake. You can roll out 2 lbs of gumpaste to a 14" piece but you might want to knead a tiny bit of shortening to the gumpaste first.
I got 1lbs to roll out pretty thick to 14"! Success! Wrapped it with plastic wrap and it’s pretty dry already. I’m going to give it a full 24 hours before I flip it over. fingers crossed
I’ll be using some keychain led lights to illuminate it. Again, *fingers crossed lol!
I wish you luck, be sure and post pictures.
Oh how did this turn out for you? Please give us a follow up.
My advice to you is to make your gumpaste
It’s too easier and less expensive
Just mix some tylose po to your fondant wilton fondant will work good