Reading nihil-perditi's post about cutting a big hole in the roof for a sun roof and questions about structural integrity reminded me of an ongoing question I have about where best to place the fan. Looks like all fans require a 14x14 opening but there is a max of 13.5 inches between the ribs of the roof. There are a longer section in front of the first rib and behind the last rib in the back but both areas have seals that'd have to be cut. So, where did all of you put the Fantastics and Maxx fans without cutting into ribs or seams? Do they really require a 14x14 opening or can the fan opening be squeezed between ribs being 13.5 inches apart?