RestKit: How does one post an array of objects?

Question summary:

Consider a class SyncObject that is KVC-compliant with properties such as: time, someValue, lastChange, uuid.

Consider an NSArray containing exclusively instances of SyncObject.

I need to submit the array to the server as a JSON array.

How would one submit this array to the server using HTTP POST using RestKit?

Example array:

[
  {
    "time": "14:45 10/21/2011",
    "someValue": "15",
    "lastChange": "14:45 10/21/2011",
    "uuid": "0b07c510-f4c8-11e0-be50-0800200c9a66"
  },
  {
    "time": "14:50 10/21/2011",
    "someValue": "62",
    "lastChange": "14:51 10/21/2011",
    "uuid": "1a6d4480-f4c8-11e0-be50-0800200c9a66"
  }
]

Details

I have an array of objects that I need to the server as JSON. It seems to me that RestKit is the easiest way to do this: I'm trying to avoid converting objects into a set of NSDictionary objects, and then using some JSON encoder to get JSON which I can POST to the server.

So, having created the array, and having set up the mapping for the class of objects stored in the array, I naturally try to POST to the server.

RKObjectManager* mgr = [RKObjectManager objectManagerWithBaseURL:@"http://localhost/someweb/api/"];
mgr.serializationMIMEType = RKMIMETypeFormURLEncoded;
mgr.client.username = @"username";
mgr.client.password = @"password";
RKObjectMapping* mapping = [RKObjectMapping mappingForClass:[NSMutableDictionary class]];
[mapping mapKeyPath: @"time"       toAttribute:@"time"         ];  
[mapping mapKeyPath: @"someValue"  toAttribute:@"someValue"    ];
[mapping mapKeyPath: @"lastChange" toAttribute:@"lastChange"   ];
[mapping mapKeyPath: @"uuid"       toAttribute:@"uuid"         ];
RKObjectMapping* mappingForSerialization = [mapping inverseM