I feel that foliage canopy isn't the only thing to consider. Also, as I believe BigCountry mentioned, the higher you go, the less your scent will affect you negatively. I climb a minimum of 20 feet. Have gone as high as 34'-38', but rarely that high. I average 24'-28'. Steep angles help with blood trails also...nothing like hitting them high on one side and having all that blood spilling from a exit hole low on the other side!