Wcf – GZip compression with WCF hosted on IIS7

Everyone, as far as I'm concerned the question is ansered in EDIT 2. Although it's only a partial solution to the IIS side of the problem, it's what I was looking for.

So I'm going to add my query to the small ocean of questions on the subject.

I'm trying to enable GZip compression on large soap responses from a WCF service. So far, I've followed instructions here and in a variety of other places to enable dynamic compression on IIS. Here's my dynamicTypes section from the applicationHost.config:

<dynamicTypes>
    <add mimeType="text/*" enabled="true" />
    <add mimeType="message/*" enabled="true" />
    <add mimeType="application/x-javascript" enabled="true" />
    <add mimeType="application/atom+xml" enabled="true" />
    <add mimeType="application/xaml+xml" enabled="true" />
    <add mimeType="application/xop+xml" enabled="true" />
    <add mimeType="application/soap+xml" enabled="true" />
    <add mimeType="*/*" enabled="false" />
</dynamicTypes>

And also:

<urlCompression doDynamicCompression="true" doStaticCompression="true" />

Though I'm not so clear on why that's needed.

Threw some extra mime-types in there just in case.
I've implemented IClientMessageInspector to add Accept-Encoding: gzip, deflate to my client's HttpRequests. Here's an example of a request-header taken from fiddler:

POST http://[omitted]/TestMtomService/TextService.svc HTTP/1.1
Content-Type: application/soap+xml; charset=utf-8
Accept-Encoding: gzip, deflate
Host: [omitted]
Content-Length: 542
Expect: 100-continue

Now, this doesn't work. There's simply no compression happening, no matter what the size of the message (tried up to 1.5Mb). I've looked at this post, but have not run into an exception as he describes, so I haven't tried the CodeProject implementation that he proposes. Also I've seen a lot of other implementations that are supposed to get this to work, but cannot make sense of them (e.g., msdn's GZip encoder). Why would I need to implement the encoder, or the code-project solution? Shouldn't IIS take care of the compression?

So what else do I need to do to get this to work?

Joni

EDIT:
I thought the WCF bindings might be worth posting, though I'm not sure if they're relevant (these are from client):

<system.serviceModel>
<bindings>
    <wsHttpBinding>
    <binding name="WsTextBinding" closeTimeout="00:01:00" openTimeout="00:01:00"
      receiveTimeout="00:10:00" sendTimeout="00:01:00" bypassProxyOnLocal="false"
      transactionFlow="false" hostNameComparisonMode="StrongWildcard"
      maxBufferPoolSize="5000000" maxReceivedMessageSize="5000000"
      messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="true"
      allowCookies="false">
      <readerQuotas maxDepth="32" maxStringContentLength="5000000"
        maxArrayLength="5000000" maxBytesPerRead="5000000" maxNameTableCharCount="5000000" />
      <reliableSession ordered="true" inactivityTimeout="00:10:00"
        enabled="false" />
      <security mode="None">
        <transport clientCredentialType="None" proxyCredentialType="None" realm=""/>
        <message clientCredentialType="None" negotiateServiceCredential="false"
          algorithmSuite="Default" establishSecurityContext="false" />
      </security>
<client>
  <endpoint address="http://[omitted]/TestMtomService/TextService.svc"
   binding="wsHttpBinding" bindingConfiguration="WsTextBinding" behaviorConfiguration="GzipCompressionBehavior"
   contract="TestMtomModel.ICustomerService" name="WsTextEndpoint">
  </endpoint>
</client>
<behaviors>
  <endpointBehaviors>
    <behavior name="GzipCompressionBehavior">
      <gzipCompression />
    </behavior>
  </endpointBehaviors>
</behaviors>
<extensions>
  <behaviorExtensions>
    <add name="gzipCompression"
         type="TestMtomModel.Behavior.GzipCompressionBehaviorExtensionElement, TestMtomModel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
  </behaviorExtensions>
</extensions>
    </binding>
  </wsHttpBinding>
</bindings>

EDIT 2:
Well for anyone else in this mysterious situation, I have a partial solution. I.e., I've gotten IIS7 to at least compress the soap messages from the service (though I now get an exception on the client, but for that there have been several solutions posted).
The problem was that the DynamicCompressionModule was not installed on my server. "Installing" it actually, for me, meant simply adding this line to applicationHost.config's section:

<add name="DynamicCompressionModule" image="%windir%\System32\inetsrv\compdyn.dll" />

(Assuming the dll exists in that directory, which in my case it did.)
And then adding the module via IIS7's Modules section for the website or server.