As others have stated, and in my opinion, there is no such thing as one specific height off the forest floor being "optimum". The terrain, available trees, under story and other considerations make the optimum height that which allows you the best unobstructed shooting lanes, while providing adequate cover ... and being high enough to mitigate scent issues. Having said all of that, I usually wind up from about 15 to 25 feet off the ground, with most set-ups being somewhere in between. I have hunted as "low" as about 10 feet and every now an then nearly 30 feet up. The low set-up was necessary because I needed to see under the crown of the post oaks where I often hunt in early November. Post Oaks, as those who hunt around this variety of oak know, are rather low growing with lots of twisted limbs. Shooting through the drip line can be tough if one is up too high, having to contend with 10' - 12' of depth of those limbs to get a clear shot at deer feeding under the oaks. The 30' set-up has been in a stand of mature yellow pines that had been managed for saw timber. The under-story was very thick and about 6' - 10' high. I had to get that far up to see clearly down and into the trails passing through that general area. Setting up at 15' simply left too many lanes covered up by the under growth.