We have 2 shorter pens that fit under the trailer side, and 3 taller ones. Gives them a lot of room to run and play (Westies) without the leashes getting tangled. Only time they are outside and we aren't, is first thing in the morning. Let them out and go start coffee. They are back inside and up on the bed long before my coffee is brewed. Otherwise they are only outside if we are as they tend to follow us around like, well, dogs.
One thing we tried that was a bad idea was putting the shorter pens under farther under the trailer, thinking they would like some more shade. Turns out that's where they wanted to poop which made it impossible to pick up. So we stopped that idea.
We even have a kiddie pool in the penned area for them.