An arc. A 120-degree arc. Shoot me your email addy and I can share a family reunion pic where I did exactly that with the Widelux. Dunno about the Noblex, but the viewfinder isn't real accurate on the Widelux, and so drafting the geometry on the ground was a much better deal than blindly trusting the viewfinder.
I had people on a radius of 11', because that's where the fixed focus is on the Widelux (I don't know the number for the Noblex). My son and I drove a stake into the ground under the Widelux tripod, then used a surveyor tape to measure out the R11' arc. Ahead of time, I trigged out what the chord would be across that arc, for 120d. I put rope on the ground where we needed people to be. Did all the above ahead of time. Then posing them along the arc was really fast, telling them what I was doing as I went. You've gotta talk with them as you go, so everybody is coached on exactly what to expect, and when, and aren't surprised when you trip the shutter.
Test the above ahead of time. Get your numbers, lay it all out at home, and take some shots with maybe your kids are neighbors at the far ends of the 120d arc, so you *know* it works. But it will.
Conceptually, the Widelux and Cirkuts work the same, both exposing film through a vertical slit. Except the Cirkut the film stays still (relative to the ground) while the camera rotates around, exposing the film through a vertical slit (which is moving in synch with the camera). The Widelux, the film and camera are stationary, and the lens turret with the vertical slit is moving.
So, same results, and Widelux pics and Cirkut pics have a very similar look - esp. if you use the 10" lens and 10" film on the Cirkut, and only rotate 120d. Widelux is 26mm lens and about 24mm height film, so pretty proportional.
Did I answer it, or just blather on way too much?