Originally Posted by Trooper
I'd do 15' as a minimum, and 20' as the maximum. While 15' is perfect, Warbonnet Blackbirds and large tarps can fill that space quickly. Maybe, try posts mounted 15' apart, but angled 15-20° away from each other. This will accentuate the distance, allowing more variables in the same amount of space.
And it will look more artistic. It depends on the room you've got of course, but I'd definitely consider going a little wider than 15'. I've got two posts in the backyard which are 18' apart, and I don't find it too difficult to reach up and put the tree huggers around at the correct height. My tarp is just over 12' end to end, and I wouldn't have a hard time imagining a wider one. Also, don't forget if you test out whoopies etc, you need some leeway at the ends, so add a foot or so each side. You'll quickly use up 15' IMHO.