Niklaus,
Thank you for your comment and for an interesting question.
While the process effectively provides a 'limit to curvature' the term itself may be more metaphorical than accurate. What happens is this:
The equivalent mass of the vortex wall, interacting with itself, produces a solenoidal C-field, just as an electric charge current produces a solenoidal magnetic field. But the increased C-field has the effect of forcing the vortex wall toward the central axis, while conservation of angular momentum increases the speed of the vortex wall. Where does this end? If an ice skater could pull her arms in all the way to a zero radius, how fast would she spin?
This is not a 'boost' situation, such as occurs in relativistic linear acceleration, so there is no natural limit, and no reason to assume that the vortex wall velocity will not reach the speed of light. If it does, what happens? I conjecture that electric charge is created at the v=c point in the process. As it turns out, the equations show that the point where this occurs is the Compton radius of the electron, that is, the 'size' of the electron as observed by electromagnetic radiation. This does not stop the vortex wall from shrinking to a point, but now there is a 'braking force' at play, since the self-repulsion of the charge increasingly resists the shrinking.
You ask about a 'natural constant' associated with this process. If one sets the C-field inward force equal to the charge self-repulsion outward force, then the point at which they are equal (and presumed stable) yields the fine structure constant, which is currently derived in no other theory.
And this 'stable' size is of the order of 10^-18 meters, a thousand time less than Compton wavelength. So the electro-magnetic field sees one size, that is associated with the v=c wall velocity, while particle collisions see a much smaller size that is associated with the final stable radius of the particle. Note that all electrons are 'identical' since one cannot even in theory observe a 'mark' on one, as the mark would move away faster than c.
This conjecture as to how charge comes into the picture is the weakest point of my theory, but compare it to string theory in which each 'winding' of the string through a 'hole' in an 11-dimensional Calabi-Yau manifold produces one unit of charge, and it doesn't appear so unreasonable. And QED simply conjectures that quantum fields, operating at a point, produce charge, but without mass, which requires a Higgs field.
I hope that explanation gives you a better picture of the process that I metaphorically described as 'limit of curvature'. It actually does limit the curvature of the C-field vortex wall, but it is due to the self-repulsion of the charge equaling the inward force of the C-field on the vortex wall.
Edwin Eugene Klingman