Actually, in anything more than about 5 knots, the gates I set are always 7 to 10 BL wide. More wind/waves/boats = wider gates.

If the course is set properly (about a 15 to 20 minute lap time), the boats will have spread out somewhat by the first gate. If there's a lot of boats, then you want a longer lap time to spread them out more. Where you get into trouble is when geography prevents you from setting a 1.7 nm weather leg (like on a small lake).