Just upgraded to U6 and getting this error on Contour forms. The max request length is set OK in web.config

<httpRuntime requestValidationMode="2.0" maxRequestLength="500000000" />

Server Error in '/' Application.
Maximum request length exceeded.Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.Web.HttpException: Maximum request length exceeded.

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace: 

[HttpException (0x80004005): Maximum request length exceeded.]
   System.Web.HttpRequest.GetEntireRawContent() +11486151
   System.Web.HttpRequest.FillInFormCollection() +261
   System.Web.HttpRequest.get_Form() +157
   System.Web.HttpRequest.get_Item(String key) +56
   Umbraco.Web.Routing.LookupByPageIdQuery.TrySetDocument(PublishedContentRequest docRequest) +67
   System.Linq.Enumerable.Any(IEnumerable`1 source, Func`2 predicate) +149
   Umbraco.Web.Routing.PublishedContentRequestBuilder.LookupDocument1() +239
   Umbraco.Web.Routing.PublishedContentRequestBuilder.LookupDocument() +226
   Umbraco.Web.Routing.PublishedContentRequest.ProcessRequest(HttpContextBase httpContext, UmbracoContext umbracoContext, Action`1 onSuccess) +187
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +80
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +270