Lets eat up 2 feet, depending on the size of the tree:
You don't have to use both slings. Use one and substitute a sort continuous loop. And a soft shackle. The continuous loop can be made shorter by doubling.
Tree strap too long? Wrap it back against the tree. No reason one end of the hammock can't be connected just to the side of the tree.
Still too long? Start on the strap on the other tree. You should be able to get a good hang with trees no further than 9 feet apart.