Hello,
first of all, if someone with a trail account wants to access the XS admin tool while using the MDC, his SYSTEM user should add all sap.xs.admin roles to his User.
But then, the settings in the xs admin tools are not enough to use no authentication for your OData.
You need to change the xsaccess file and create an xssqlcc file, like in this Thread.
I hope this may help someone else, greetz! 