I have used a wave 3 for a couple years. I live at 7000 and travel to 9000. I leave the vans front window open a crack and the rear also - meaning an inch. Then run the heater on low. My caveat is not to leave it out in the rain. The fix is around $150
Spent 3 months living in my regular van. No high-top. Just fine for us. When you have a kayak on top getting it on and off is easier with a regular van.