Call member services and ask them. If they say it is OK, then you have an official answer that you can use.
You may not be aware, but a little history is that this is an ongoing aurgument on these boards and most times the moderator ends up having to close the thread because the back and forth gets out of line. A recent poll among posters showed that the majority (2 to 1) favor allowing 5 in a one bedroom (sometimes with stipulations). The poll upset those who oppose, and there was a couple of individuals who actually ended up sabotaging the thread beyond the moderators warnings in order to close the poll whose results they didn't like. There are also posters who seem to just like to aurgue for aurguments sake.
But non of that really matters, what matters is the answer that Member Services provides you. They legitimately have the discretion to allow the additional occupancy when they determine it is appropriate. Many posters are reporting that members services is accomodating to thier request of an additional person. My poersonal opinion it that their decision to allow 5 is entirely appropriate.
But I won't aurgue the point here, I just wanted to pass along the advice to call MS and to let you know that you shouldn't take the postings here too seriously especially if your unaware of the heated debate and closed threads that arises every time this issue is brought up.
Have a wonderful vacation.