Sorry to be late, but I just found this conversation. I guess I don't understand the concept of "recoverable deadspace". I appreciate that there is some volume (but not all) that can be drained from under the false bottom by the center pickup tube. But true deadspace is, by definition, unrecoverable.
So I just use zero for "recoverable deadspace". As a simple test, I filled my MT with water a few inches over its drain port on the kettle wall, and then ran my pump as if I was draining wort. When the pump sucked air, I shut it off and then tipped the kettle to collect and measure what was left -- the "unrecoverable" deadspace volume.
Is it more complicated than this? Am I missing something with this "recoverable deadspace" term?