I've been doing DDP Yoga and love it. I've noticed a big difference in my knees and overall flexibility. It was created by ex wrestler Diamond Dallas Page.
http://www.ddpyoga.com/
I used one this year elk hunting and loved it. I never felt that it was in my way when climbing. The one thing I did notice after using it all day was that I could feel it on my hip since it attaches to your waist belt. But it was better than using a sling.
I have the T1 and use it when I'm out hunting during the day. It packs down small enough for me and you hardly feel it on your back with 10 to 20 pounds in it. Plus, I can use it to haul meat back to camp if I get an animal down.
It seems we always get back to camp late and all we have time for is to eat and go to bed. I love to have a fire if I have time. I've never noticed it affecting the animals. I've had a group of elk come right through camp once while we were sitting around the fire.
I remember hearing the story of San Diego Charger's Doug Miller who was struck by a bolt of lightning in the high country in Colorado. While they were trying to get him breathing again he was struck by a second bolt.
I take what the good Lord puts in front of me. If I can see the bull I may pass on a cow. We don't eat the antlers in my family. Any elk down is good for me.