I use PMG Messiah for most of my rendering and rigging but it is not an option to select for what software is used on the render. Irony is that there is a Messiah forum here one would think that it would be an option due to that. I think it is probably an oversight that was not brought to anyone’s attention.
As a side not I uploaded my final challenge entry I did not get an option of uploading a Tiff via FTP. I did upload a properly sized JPG with minimal compression for it hope that is enough.