Is this in leu of Louise walking down the aisle?

They make brake blocks for zip lines that will help slow you down near the end… the “in line brake block” here http://ziplinehomekits.com/parts.html is the one I use, although you can buy them anywhere…

Of course, hitting the ground in the middle is harder to fix… you either need to raise the start and/or finish height, grab a shovel or backhoe to re-grade, or increase cable tension. Be careful adding too much tension, as the forces created by one person’s weight are greatly magnified as tension is increased.

Good Luck!