planks @60 - the problem is that I don't have the necessary G anywhere suitable in the grid, regardless of which S I choose. (Is there a choice?) The only G is in the title of the poem. Do I have an incorrect entry somewhere?
unclued @61 - yes, the eight words (two of them of only two letters) explain how to visualise the information in the structure. Like you, I doubled two Es and an M, which means that the elusive G doesn't have to be added to what's there.