You may use a short bungie attached to the line to maximize the drag on bigger fish or to put some pressure on a holed up fish. That set up is called a "flungie" by the late Nathan Lee

If you´re targeting bigger fish in open water a bungie is the way to go.
A float line too narrow is prone to entaglements, one too thick is a p.i.t.a. Make it in a bright color as Don previously stated, is a great way to locate a spearo from a boat.