So you probably know that if you have a multi-client LightSwitch project that you can set the default client that gets launched when you F5 by right-clicking on the desired client project and selecting "Set as StartUp Client"

 

And, you probably also know, that this setting does nothing in the deployed app...

 

Well, the good news is, the settings "wants to" work, it's just getting trumped by a competing force.  I won't get into the details, I will just show how it can be fixed.

Ready?  It's pretty involved....

Open the web.config file in the Server project.  Find and remove this chunk and save the file:

I have logged a bug for this and it should be fixed in a future release.