Hi Robert,
The public mocha forums found at Imagineer are still down (will be restored in the future).
mocha support team can still be contacted direct by using the support contact form:
If I am understanding your question, you should be able to duplicate your mocha layer, leave the surface in the position that you want, than simply re-track. (duplicate layer icon underneath layer controls OR CNTRL D).
As far as I know, the surface coordinates is not something currently exposed numerically to the user. If you saved the AE corner pin tracking export format and viewed the file, you would find the corner coordinates - but there is nowhere within mocha to enter them. For version 4 of mocha we are working on adding Python support and scripting, so users will be able to do more with the data and exports.
Hope this helps.
-Ross