Forgot my password and had to post under slightly different name.

Thank your for the replies!

Went back to HD this morning. The "heavy duty" Stanley 4 inch barrel bolts have 5/16 inch diameter bolts and have a 7/8 inch "throw". The standard duty Stanley 4 inchers also have a "throw" of 7/8 inch, but the bolt itself is smaller (1/4 inch diameter). The housing of the heavy duty model is made of heavier steel and the screws that they give you are longer.

As was recommended on the noaa web page, I was going to discard the screws that they give you and use 1/4 inch hex head bolts and washers. I will use 3/4 inch exterior grade plywood.

On the websites of companies selling hurricane hardware that I've seen, they sell barrel bolts, but they don't tell you if they are heavy duty or not, and they don't give barrel diameter or throw.

I like the idea of putting the bolts closer together and I believe that this is what I will do.

My house is brick veneer construction. The brick is red clay and I recently discovered that it is hollow, with two cells per brick. House was constructed in 1997.

I have twenty five windows, two doors, and the double front door to cover. I believe that two of the windows and the double front door are too big (7 feet tall, 7 feet wide) to use plywood/barrel bolts, so I may have those shutters professionally made.

Haven't decided what to do about the two metal garage doors , which I understand are inherently weak.