What do you mean by 'outside cells' muraria? Each of my rows six and seven has two bars, in identical positions and narrower than the ones immediately above and below. Is that correct?
Update on my numbers: because of a post I saw (and possibly misunderstood) yesterday, I was counting the top row of the grid as part of the structure. I'm now thinking that's wrong, but still can't reconcile the numbers. I'm getting 41 now.