We are in the process of finishing our 7,000 sq.ft studio in Phoenix, and I had the same question about the best way to build a cyc. Most of the photographers here in town had a set builder just make it for them, and theirs are made out of 2X4's, a 45 degree support beam underneath, a piece of sheet metal that is curved, and drywall. However, this is not the most durable way to make it, and is also very permanent.
We wanted a solution that was lightweight, strong, expandable, and portable if we ever decided to move. I called Pier 59 Studios in New York and the guy that built all of the cycs there was very helpful. They bought all of the pieces from Calumet (Infinity Walls) and they had been very happy with its ease of installation and durability.
I called Calumet and talked with a sales rep, and he said that quite a few of the biggest studio complexes in the country use their product, and that convinced me to purchase the product. When we received it, I was amazed at its flexibility and strength. It comes in flat sheets four feet wide, and is a fiberglass/PVC blend. As you bend it, it actually becomes stronger because it resists against you, and is a wonderful material.
Our studio is a tilt-up concrete building, and the cyc needed to be formed between a concrete wall and a concrete floor, not a 2X4 wall like most studios. We put up two rows of furring strips (one on the wall and one on the floor) as a guide to hold the strips in place while we drilled them into the walls. Once they were in place, we removed the furring strips and filled the seams with drywall mud. We also began to feather the curve into the floor and wall with drywall mud. It takes about 3-5 coats of mud to get a perfect curve from the lip of the material to the floor and wall. One day of work, and then two more days of feathering the mud and letting it dry and our work was done.
The cyc looks amazing, has no imperfections, and is as simple as it gets. I even tried stepping on it, and all that happened was the drywall mud separated from fiberglass slightly, but was unnoticeable once I took my foot off. I would highly recommend this material, and if we want to we can unscrew it and take it anywhere.
For comparison, we also looked at Pro Cyc and Sinar Bron, and I'm sure they would have been just as good but their quotes were double that of Calumet. Hope this helps,
Brian
Loft 19 Studios
http://www.loft19.com