+1 to John's point and your initial troubleshooting approach.

Try adjusting the Web.config of the Session Preview (OData) webservice again--maybe double it until it works and/or confirm how much content (and maybe multimedia) is used by that page. Or try a smaller page. :-)

This [StackOverflow post points out two settings][1], one for ASP.NET and another for IIS 7; multiple users also point out the difference in measurement unit (KB for .NET, but bytes for the IIS setting).

http://msdn.microsoft.com/en-us/library/e1f13641(v=vs.100).aspx

    <configuration>
        <system.web>
            <httpRuntime maxRequestLength="size-in-KB" />
        </system.web>
    </configuration>

But also:

http://msdn.microsoft.com/en-us/library/ms689462%28VS.90%29.aspx

    <system.webServer>
       <security>
          <requestFiltering>
             <requestLimits maxAllowedContentLength="size-in-bytes" />
          </requestFiltering>
       </security>
    </system.webServer>


Maybe someone else can fill in the details of what gets sent to Session Preview storage. I'm guessing it's the session-specific page, component presentations, and multimedia but haven't checked to be sure.

  [1]: http://stackoverflow.com/questions/3853767/maximum-request-length-exceeded