A man in our neighborhood has used a different method of putting up plywood that looks a lot faster. My husband says it's not safe because it puts the plywood up next to the glass. (I need to throw in here that we are fairly recent residents of FL and have not really had an experience with this until now). The man told me he read about this method on the national oceanagraphic web site. Anyway, what he did was put bolts on the plywood and then drill holes in the concrete surrounding the window to slide the bolt in . When he wants to take them off he just unbolts them and takes them down. The plywood has been cut to fit just the glass part. The bolts have four screws holding them and he has one on each corner.
The only directions I've seen have been on a newspaper web site and says use plywood four inches larger than the window .