I've also just started experimenting with derived models.
In the 5.5 Derived Model Support documentation
Fetching DTO instances
To fetch DTO instances, the projection methods are used to append a projection to a Linq query formulated in an IQueryable<T>. Below an example is given of using these projection methods, by fetching a set of Customer DTO class instances projected from a set of Customer entity instances, using a Linq query. The Customer DTO class instantiated is given in the Generated DTO class structure section.
Does this mean that if I am using QuerySpec I have to do an In-Memory projection? Or did I miss the QuerySpec section of the documentation?