You need to go to this URL for the correction of the leaking rear windows.
http://www.rialtainfo.com
Look under modifications, VW and coach.
Look under sagging Rear side windows for the PDF file that shows how to remove the side windows and reseal them from water leaking. Winnebago did not place any shims under the side windows to keep them from sagging over the years. When they sag, it looses the seal of the butyl tape and therefore leaks at the top of the window.
Many members have done this repair over the years and has proven to be the correction of leaking side windows.