With trees 25' apart, you'd have to have your tree strap connection VERY high in order to get sufficient sag. For an optimal 30 degrees, you'd have to be around 9 feet above the ground.
It's worth playing around with to see if it will help. In my experience, 25 feet is a LOOOONG distance for hanging.
"The more I carry the happier I am in camp; the less I carry the happier I am getting there" - Sgt. Rock