Yeah, that bottom bunk gets stuffy. I'm currently planning to mount a fan, but I really like the tension rod idea! I didn't even think about the water heater! DOH! Mine sits under the back corner of the bottom bunk.
2014 Jay Flight 28 BHBE
2015 RAM 2500 6.4L HEMI, Tradesman 4x4, 3.73
Blue Ox SwayPro (BXW 1503)
Upgraded from an REI internal frame backpack and a Eureka 1/2 dome tent!