So I hate the look of the antenna on the roof, just think it ruins the fine shape of this car... anyway I used a Carbon Fiber Console Plaque. It was meant for that purpose but I changed a design. So I bought the center plaque from
http://www.innovateddynamics.com/pro...-holder-plaque
For $15 it is a steal. It's hand made to order. So I decided to give it a try using it to use as a cover for the hole well it worked. I plan to paint it when the weather outside allows as I do not have a garage. So it can be very easy or slightly difficult. Easy version, remove old antenna, clean area the size of the plaque use 3M DS tape and add silicone sealant around the rectangular hole for peace of mind and done!
For even more peace of mind I epoxied a 3/4" long 1/4-20 thread cut off a bolt. This takes more time and I secure it with a flat washer and wing nut. Overkill but I'd rather make sure it doesn't fly off. But tape should be fine.
I will upload more detailed pics later but here's the result before I paint it this spring. I have the simple install instructions in my build thread page 12