It has come to my attention that the link for Ortho_gt was broken (thanks @ Keith Lang). I've updated the download, and it's available - here.
In the proto-QC, Pixelshox, changing the projection matrix worked by creating a layer style render patch, which would be placed "under" patches you wanted it to change the matrix for. This still works in QC, and can be used in the QCPlugin api, where environment macros are not able to be made in the same way the unofficial api provides for.
The default parameters may not appear to change the projection matrix. I chose them to look fairly similar to the aspect ratio it will have before it's engaged. Manipulate left, right, up, down, and it should be obvious that things have changed. This has only been tested in OS X 10.6 and 10.7.