Hi Mauro - there is a bug in the first v3 beta with curve-to-curve based flow where it produces a very heavy and slightly wiggly result if you have the curves in any orientation other than flat on the world x/y plane.

So for the moment to avoid the problem rotate your curves so the base curve and target curve are both flat in the world x/y (top view) plane and then you should see it behave better.

That is a bug that I've just fixed up for the next v3 beta.

- Michael