I have built a few tops.......some looked like carson tops, and others like a regular convertable top.
It is really easy and pretty cheap.
All you need is electrical condutit pipe, a electrical conduit tubeing bender, and a tubeing cutter. Then go to a boatshop and buy Top bracket hinges. The conduit fit's perfect, you just measure the width of your car..........bend tubeing to a 90' and cut to the heighth of the windshild. Slip the end into the swivel hinge and tighten the set screw. And if your doing like a carson style top, start your first bow behind the door.....and you can run a piece of masking tape from the top of the windshield frame.....to the first bow.....then you can run the tape beyond that to figure out where your going to put the next bow to achieve the profile that you want.
Then all I would do is have the upholistrey shop make a top, with sleaves that will snap around the bows. And put snaps around the base of the top, and on the front of the windshield frame, so the top wraps over it. And when your not useing the top.........just snap the covers over the snaps that are on the body. They come in many colors......or you can paint them to match your color. I useally pay about 175.00 for a water proof top in black or white.....with a narrow oval mailbox slot rear window, made out of clear vinal.
Some boat shops can do your upholstrey for you......Iv'e found some to be even cheaper than a regular upholistrey shop.
Hope this helps.