Multiple php.ini with IIS6 and ISAPI PHP4

To allow multiple independant php.ini configs for different sites on the same IIS6 box I have been using the cgi edition of PHP4 and it all works well. Each has its own PHP4 install with php.ini it the folder holding the cgi binaries. The default search path checks the binary location first and the custom php.ini is loaded. The downside is upgrading PHP versions requires work for each site and a very busy site is going to put a lot of extra load on the box. Has any work been done to allow a custom php.ini per site under the ISASPI version in IIS6? Regards Petar