As of Version 1.6.1
The class HttpEventCollectorSender has a private member named "serializer" of type JsonSerializer that gets configured correctly in the class' constructor, however it is never used: later in the same class, a plain JsonConvert.SerializeObject() call is made (methods SerializeEventInfo and DoSerialization).
That means that the globally-configured json serializer is used instead of the ad-hoc one.