I worked at Download last year on traffic and car parks and that tent looks to big for our staff campsite.
I think the best thing for you to do is to ask the regulars that go there every year on the Download forum.
https://forums.downloadfestival.co.uk/login/
Sorry can't answer but I vaguely remember a festival (sure it was this one but could be wrong) that restricted tent sizes to +1 occupants ie 5 people in max 6 person tent or 2 people in max 3 person tent, not exactly fair as a 3 person tent generally doesn't have a living area.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.