Those of you who have extenders or extra long whoopie slings, how high up the tree do you have to set your tree straps. I know with a normal hang (~15ft between trees) straps need to be about 6 ft off the ground. However Knotty mentioned 12' whoopie slings which would give a total tree to tree of somewhere over 30'. Are your tree straps 10' off the ground or am I missing something here?