Use custom domain with setup

Hi, I tried the forum search, but I didn't find an answer.

I have installed Domain Mapping and it works fine.
Now I want to choose the custom domain with the setup of a new blog - ist this possible?

I was able to change the subdomain to the custom domain after the setup, but then the Fileupload Url still pints to the subdomain of the network root.

Thank NAME, for their help.

Let NAME know exactly why they deserved these points.

Gift a custom amount of points.