Hi @maccayk ... we have an 'add a room' on our 12 footer ... comes in real handy for longer stays (small awning!) but we don't worry about using it for weekenders though
We had one with our 16, great for storage and putting things out of sight at night time. Ours was known as the dunny room as this was where our porta potty was! Easy to put up once you've done it but 2 people makes it easier. I also bought a small silver tarp for the roof and punched eyelets in to match poles so I could keep the top clean.
Bikes, beach gear and dunny. We think worth it's weight in gold, no midnight visits to toilets with young daughters requiring parental assistence. We didn't have a toilet to start with, but now we do, would never leave home without the extra room.