I imagine it would depend on the dealer. I didn't have to give money down at all to order mine, and didn't sign any papers.
However, given that they are selling like hot-cakes, I'd think it shouldn't be a problem. It's not going to sit on their lot for very long.
In fact, I changed my order to add something after it was too late to affect my order. The car had been "pulled" and was going to be built and delivered to the dealer anyway. Instead of being annoyed with me, they thanked me because I just gave them an Explorer to sell off the lot.