I'm working on several issues that appeared in our org with the introduction of the Summer 18 preview. We are using SFDX and scratch orgs for development. I've figured out how to create a scratch org that is on Summer 18, but it required that I create a Enterprise trial org with Summer 18 and set it up as a Dev Hub. So I've done all that and created a scratch org successfully, but I'm having difficulty pushing our code base to it. The long list of error messages seem indicate that it doesn't know that any of our custom objects and fields exist. I'm suspecting that it has something to do with the name space not being different from our code base and the scratch org I'm pushing to? I've found the following article that I believe says I need to link the name space from our current Dev Hub, to the new Dev Hub I've created for Summer18.  
https://developer.salesforce.com/docs/atlas.en-us.sfdx_dev.meta/sfdx_dev/sfdx_dev_reg_namespace.htm

Am I reading that I can create a name space link from one Dev Hub to another or can a name space/Dev Hub only be one-to-one? It seems I need to find some way to push my code base with our current name space to a scratch org based off of the new Dev Hub that is on the Summer 18 preview. 

Any advice or experience is welcome, thanks.