I generally use stands between 12' and 20' depending on the situation. I have one stand that has the foot platform just 10 feet off the ground because of where it's located and the tree it's in has huge branches coming off the tree just below the platform. I may be hidden in that stand better than most of my others. I got nervous just reading that last part. Be careful out there!
That is the beauty of my Summit Vipers. I have that rail for security and to lean against when I shoot. About the only way I could fall is for the stand to suddenly decide to fall apart.
D Depends upon how much cover I have, but my stands with lots of cover I have no problem 10-15, without cover I like to be a little higher 15-20