smithsax - I would only consider placing letters outside of the grid if there was a thematic mechanism for dropping the relevant scoring letter from an answer and moving it outside of its non-word entry, and there isn't such a mechanism.
There are 17 scores and 3 no scores, all dictated by the presence or absence of the scoring letter in their answers - I can see no reason to add the scoring letter to any of the no scores, their answers would then become non-words.
A requirement of the preamble is that there are 16 locations, I can see no other way of achieving this other than by having 4 locations in the central area. This requirement has become necessary because, as I tried to argue earlier, the grid is slightly compromised to make it functional.
I think we are given enough information to arrive at a correctly filled grid, the only issue seems to be - how are the two scoring entries in the 6th ring to be treated? The preamble could have been clearer in this respect but nothing in it suggests a mechanism for disqualifying a scoring entry.