Best PA for guiding

I believe that this is now done, and tested via the OT and a test case.
(We may wish to add more test cases for this?)
Is this more, though, than we wish to do for the estimate method? It seems, then, that this is doing as much as the select method.

I'm not 100% clear on how this estimate method should be functioning. I'll check in the new code in a second and if you could take a look at it, I would really appreciate it.