Hello Shimpy, hello everybody! newbie here! like other people before me, I just found this thread and I am sad I didn't it before....oh well, at least I'll be able to comment a few things from the last pages.
An interesting thing I noticed, it's the fact than at least in the show, if it does NOT happen in the Trial of Seven, Cleganebowl will make more sense if it is related to Arya, because, at least in the show, it seems she is the most important person in Sandor life, and Gregor is in her list too.