The cuben fly I made doesn't use cat curves where the panels join, but it does use a lot of arbitrary curves, since it fits on a 3D dome shaped tent. If you flipped the fly inside out, some of the curves might be similar to a cat curve it seems. I would feel reasonably comfortably trying to make a cat curve tarp using a similar technique.
To join the two panels to create a curved 3D shape, I used a liquid adhesive. Theoretically you could use tape, but a slow-ish drying liquid adhesive gives you time to improve the work before it dries. I think it would be hard to use tape and not wind up with at least a few large wrinkles unless you practiced a lot. I'm not sure how the cottage manufacturers do it with tape.
To start, I cut one half of the material exactly to shape, and I cut the other half with an extra 1" of material which acts as the bond overlap. You could do 1/2" of overlap on each, but I figured this was simpler and accomplished the same thing. I drew a line with a dry erase marker on the second piece of material one inch in from the edge, so that I knew where to line-up the edge of the other piece. Dry erase marker comes off easier on one side of cuben than the other, so do some tests first before you draw a fat line down the material that might not come off.
To actually bond it, I used Hysol liquid adhesive and I worked slowly from one end to the other to get it bonded. Make sure to keep the fabric lined up, by putting a few ticks along the way that should line up. You don't want to get to the far end and find out once piece of material sticks out 2" further. Once it was bonded, I went over it a few times to smooth out any large wrinkles into a few smaller ones etc. As long as you keep the wrinkles small, it goes together well. The wrinkles can be pressed down and if you go over the seam every 30-60 minutes for a few hours to make sure it's all pressed down then you'll get a nice result. If for some reason you weren't happy, you could try adding one sided tape over the seam on one or both sides afterwards but I don't think this is necessary.
Here is an example of a curve I did on the cuben tent fly:
I suspect a 1" seam isn't totally necessary. A 3/4" overlap would look nicer, be lighter and have less wrinkling. I have done any scientific tests, but a 1" overlap seems like it may be overkill. Here is an example of a curve using a 1/2" bond. Since the bond is narrower, you can achieve a significant curve with not much wrinkling: