You've seen it before, perhaps on your own car cover-a big hole (or holes) or a long slit to accommodate the antenna because you weren't able to accurately target the right spot. Locating the opening on a new cover can be tricky, but a little studying and measuring can help you position the hole perfectly on the first try.
By installing the cover on...
By installing the cover on the car except for the antenna area, you can determine the location for the antenna opening by using the seams as a guide. Mark the spot with a pencil. NPD's Rick Schmidt says it's better to spend an extra five minutes making sure of the location than to end up with several holes or a long slit.
On newer Mustangs, simply unscrew the antenna, correctly position the cover on the car, and mark the location for the opening. However, because it's difficult to remove the antenna mast on vintage Mustangs, we've got a tip from CoverCraft.
First of all, don't try to locate the hole by stretching your new cover over the antenna. That's a guesstimate at best because the height of the antenna doesn't allow the cover to lay in its proper position.
We followed CoverCraft's instructions for our Evolution cover and it worked perfectly. First, place the cover on the car; on the passenger side, allow the cover to drape around the antenna. Elsewhere on the car, center the cover and align the seams with the fender edges and roof. On the passenger-side front fender, carefully pull the cover as close as possible to the antenna base. That will give you an idea of the antenna location. You can also compare how the seams line up on the other side of the car, which should be properly positioned. Most seams will run along the top edge of the fender. On the passenger side, you can use the seam as a distance guide by measuring the space between the edge of the fender and the antenna.
Why don't car cover manufacturers provide covers with the antenna opening already there? Rick Messmore from CoverCraft explains that vintage Mustangs were shipped to dealers with the antenna in the trunk to prevent damage during transit. Although a template was provided, dealer service departments didn't always install the antenna in exactly the same place, which makes it difficult for car cover manufacturers to know where to put the opening.

After removing the cover from...

After removing the cover from the car, use scissors to trim a 3/4-inch hole in the marked location.

CoverCraft provides a two-piece...

CoverCraft provides a two-piece plastic antenna grommet with its covers.

With the cover sandwiched...

With the cover sandwiched between the smaller "spiked" ring underneath and the larger ring on top, use a rubber mallet to snap the two rings together.

Following CoverCraft's directions,...

Following CoverCraft's directions, we were able to perfectly place the antenna opening for our Evolution 4 cover.
Cleaning a Car Cover
Most car covers are washable, which will allow you to clean your cover to remove dirt and dust that can build up in the fabric over time. A clean cover will help keep your Mustang clean and increase the life of the cover.
It's best to follow the cleaning instructions that come with the cover because the different materials require different cleaning processes. CoverCraft recommends never cleaning a car cover in a washer with a center agitator, nor should you use a fabric softener. Avoid the temptation to dry non-woven covers in a dryer; they should be allowed to air-dry because dryer heat can melt the polypropylene fabric.
CoverCraft's general instructions say to use a washer without an agitator (bulkier non-woven covers will likely require a large commercial washer). Place the cover in the washer and add 1/4 cup of Simple Green All-Purpose Cleaner after it's filled with warm water. Use the gentle cycle if available. After washing, rinse the cover twice to remove all of the cleaner, then air dry.