We learned the hard way not to leave our dog at large in a camper. She found and ate a chocolate candy bar (wrapper and all) while we were away for 15 minutes. After some induced vomiting, she was okay. But it made us think about what if she jumped down from the bed and broke a leg while we were away for a couple of hours. Not an acceptable option for us.
So we now leave her in a well-ventilated soft carrier which gives her plenty of room to stand and turn around. She loves it. Gets in on her own when told to do so because she knows she'll get a treat for doing it.
Still, we try not to be away more than two or three hours. Anything more and we leave a camper key with friends or campground owners (if we know them well) who can get inside in case of a power failure or other emergency.
The carrier stays on our bed during the day, so it doesn't get in the way of normal activities. At bedtime, we move it to the dinette, and we put it back on the bed in the morning. No problems with it taking up too much space. Might not work with a real big dog, though.
2013 Surveyor SP220
2010 Silverado LT 5.3 V8
The world is a great book, of which those who never stir from home
read only a page. - St. Augustine