I've read totally opposing opinions saying both that there should and shouldn't be any play in the spreaders. Any opinions? If so, vertical or horizontal?
The spreader should bisect the angle of the shrouds. If there is any vertical play the force on the spreader will be bending rather than compression with the risk of failure if carried to extremes. Horizontal play is generally OK. Some boats have pivot pins at the spreader root. Pivoting will allow the spreader to line up with the shroud and avoid any bending moment.