PowerShell remoting with a one-way trust

My question is similar to Powershell Remoting: One way trust, however there are differences and the resolution (adding the server to the trusted list) does not work for me.

Scenario:
I have two domains. DOMAIN and DOMAINDMZ. DOMAIN has an incoming trust from DOMAINDMZ. That is DOMAINDMZ trusts DOMAIN, but not vice versa.

I have an administrative user DOMAIN\myadmin who is a member of the Administrators local group on several servers in the DOMAINDMZ domain: servera.domaindmz.com, serverb.domaindmz.com, serverc.domaindmz.com, etc. I can log into these servers with DOMAIN\myadmin from the console or RDP.

I am attempting to log into SERVERA and run a PowerShell script on SERVERB using PowerShell remoting. Remote Management is enabled on SERVERB. I start an elevated PowerShell session on SERVERA, and then attempt to use the Invoke-Command cmdlet. I receive the following error:

PS C:\Windows\system32> Invoke-Command -ComputerName serverb.domaindmz.com -ScriptBlock {hostname}    
[serverb.domaindmz.com] Connecting to remote server failed with the following error message : WinRM cannot process the request. The following error occured while using Kerberos authentication: The network path was not found.
     Possible causes are:
      -The user name or password specified are invalid.
      -Kerberos is used when no authentication method and no user name are specified.
      -Kerberos accepts domain user names, but not local user names.
      -The Service Principal Name (SPN) for the remote computer name and port does not exist.
      -The client and remote computers are in different domains and there is no trust between the two domains.
     After checking for the above issues, try the following:
      -Check the Event Viewer for events related to authentication.
      -Change the authentication method; add the destination computer to the WinRM TrustedHosts configuration setting or use HTTPS transport.
     Note that computers in the TrustedHosts list might not be authenticated.
       -For more information about WinRM configuration, run the following command: winrm help config. For more information, see the about_Remote_Troubleshooting Help topic.
        + CategoryInfo          : OpenError: (:) [], PSRemotingTransportException
        + FullyQualifiedErrorId : PSSessionStateBroken

If I provide a credential object containing a user in the DOMAINDMZ domain, the error goes away and the scriptblock executes as expected:

PS C:\Windows\system32> Invoke-Command -ComputerName serverb.domaindmz.com -Credential DOMAINDMZ\Administrator -ScriptBlock {hostname}
SERVERB

Question:
Given the error I suspect the issue is related to the trust and Kerberos, but I'm not clear what I can do to resolve. Should I be setting an SPN for DOMAIN\myadmin or SERVERB? Is there something else I can try?