I've been researching buying one of these for our elk hunt this year in WY. We've been spoiled in CO because there's a shower house at our campground and another at some cabins you can pay to use. The only bad reviews I've found is a few people have said they will not heat well at altitude. Our base camp will be around 8500 so im thinking we will be fine. Also there is a zip model and a instant model which is red. Both I've read the trick is to recirculate the water to get it hot. Any suggestions?