Hi, thanks for posting!
The correct way to do this is to specify
ExclusivelyUsesAttribute at assembly level of the test projects you wish to disable parallel execution on.
Simply specify it with an arbitrary value, i.e. [assembly:NCrunch.Framework.ExclusivelyUses("TestRunner")]
All tests within these projects will then be marked as making exclusive use of the "TestRunner" resource, and will not run in parallel with each other.