Thanks for the info PJ!

PCT looks very interesting and your EPIC goal framework strikes me as intuitively plausible. The current list of IGs that we reference is not so much part of CT as an empirical finding from our limited experience building CT charts. Neither Geoff nor I believe that all of them are actually intrinsic. It is entirely possible that we and our subjects are simply insufficiently experienced to penetrate below them. It looks like I've got a lot reading to do :-)