Umbraco Cloud Migrate Solution - Must I use UmbracoProject or can I specity solution file?

I am looking at the git repo generated when I created an umbraco cloud project. I see the following in the .umbraco file:

[project]
base = "src/UmbracoProject"
csproj = "UmbracoProject.csproj"

Since I have an existing project src/MyUmbraco.Site in a solution that has other library project, Can I switch the .umbraco file to something like?:

[solution]
base = "src"
sln = "MyUmbraco.sln"

Where the solution contains the MyUmbraco.Site project and the library projects.

Or must I rename the project to UmbracoProject? Do I need to do something else to add the library projects?

UPDATE: Both of the answers below are correct. I marked the second one as the answer, because I used the nuget package to generate a multi project solution; that showed me what should be in the .umbraco file. The structure of the .umbraco file should reference the project file and not the solution as I was guessing above:

[project]
base = "src/CustomProjectFolder"
csproj = "CustomProject.Site.csproj"

This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/113521-umbraco-cloud-migrate-solution-must-i-use-umbracoproject-or-can-i-specity-solution-file