You can add the necessary configuration to the .dnn file:
1) Be carefull that you do not step on another service though!
2) There can be only one System.ServiceModel section:
3) My example WILL step on other services (so this needs to be modified to not do so.
<component type="Config">
<config>
<configFile>web.config</configFile>
<install>
<configuration>
<nodes>
<node path="/configuration" action="update" key="name" collision="overwrite">
<system.serviceModel>
<bindings>
<basicHttpBinding>
<binding name="BasicHttpBinding_IUser" closeTimeout="00:01:00"
openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"
allowCookies="false" bypassProxyOnLocal="false" hostNameComparisonMode="StrongWildcard"
maxBufferPoolSize="100000000" maxBufferSize="100000000" maxReceivedMessageSize="100000000"
textEncoding="utf-8" transferMode="Buffered" useDefaultWebProxy="true"
messageEncoding="Text">
<readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
maxBytesPerRead="4096" maxNameTableCharCount="16384" />
<security mode="None">
<transport clientCredentialType="None" proxyCredentialType="None"
realm="" />
<message clientCredentialType="UserName" algorithmSuite="Default" />
</security>
</binding>
</basicHttpBinding>
</bindings>
<behaviors>
<endpointBehaviors>
<behavior name="endpointBehavior">
<dataContractSerializer maxItemsInObjectGraph="2147483647"/>
</behavior>
</endpointBehaviors>
</behaviors>
<client>
<endpoint address="your endpointaddress"
binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding_IUser"
contract="WWWUser.IUser" name="BasicHttpBinding_IUser" behaviorConfiguration="endpointBehavior" />
</client>
</system.serviceModel>
</node>
</nodes>
</configuration>
</install>
<uninstall>
<configuration>
<nodes>
<node path="/configuration" action="remove" />
<system.serviceModel>
<bindings>
<basicHttpBinding>
<binding name="BasicHttpBinding_IUser" closeTimeout="00:01:00"
openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"
allowCookies="false" bypassProxyOnLocal="false" hostNameComparisonMode="StrongWildcard"
maxBufferPoolSize="100000000" maxBufferSize="100000000" maxReceivedMessageSize="100000000"
textEncoding="utf-8" transferMode="Buffered" useDefaultWebProxy="true"
messageEncoding="Text">
<readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
maxBytesPerRead="4096" maxNameTableCharCount="16384" />
<security mode="None">
<transport clientCredentialType="None" proxyCredentialType="None"
realm="" />
<message clientCredentialType="UserName" algorithmSuite="Default" />
</security>
</binding>
</basicHttpBinding>
</bindings>
<behaviors>
<endpointBehaviors>
<behavior name="endpointBehavior">
<dataContractSerializer maxItemsInObjectGraph="2147483647"/>
</behavior>
</endpointBehaviors>
</behaviors>
<client>
<endpoint address="your endpointaddress"
binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding_IUser"
contract="WWWUser.IUser" name="BasicHttpBinding_IUser" behaviorConfiguration="endpointBehavior" />
</client>
</system.serviceModel>
</nodes>
</configuration>
</uninstall>
</config>
</component>