Hi Robert,
Yes, this is one of the limitations of the saveMWF() API method. If you want to continue to use the temporary redline functions, you could also use Dynamic Authoring Toolkit. Using DAT, set your map min and max coordinates to what the user desires for that area. This would require that the user choose an option to start redlining prior to any redlining. Then, DAT would produce the map with the proper bounding area from their current area, pass the MWF back to the interface, then they would start redlining and save the MWF.
A more permanent solution would be to use server-side storage of redline objects which would also store coordinate information for "areas of interest" in an application database. They could then pull up these areas later. This is a fairly large programming endeavor, but works very well.
Andy Morsell, P.E.
Spatial Integrators, Inc.
http://www.spatialgis.com