SP configuration on IIS (ISAPI) and preservation of POST data

[Bobby Lawrence]

So we've been using Shibboleth for a while now and are very pleased.
We are running the SP (version 2.4.2) on IIS.
However we've noticed that when someone submits a form POST after their 
session has timed out, when they are redirected back, the POST 
parameters are missing and the page usually ends up in an error because 
it was expecting a POST and instead its receiving a GET.
According to the docs 
(https://wiki.shibboleth.net/confluence/display/SHIB2/NativeSPSessions), 
there are a few options that allow the SP to preserve the POST 
parameters in a StorageService for replaying after authentication 
(postData, postLimit, postTemplate, postExpire).
However, whenever I test this, I always get an error.  The native.log 
file has this message:

ERROR Shibboleth.ISAPI [3084] isapi_shib: The request's Content-Length is not available to an ISAPI filter.

Is this a feature that isn't supported on the ISAPI version of the SP or 
something ?

-- 
Bobby Lawrence
MIS Software Developer
Jefferson Lab (http://www.jlab.org)
757-269-5818