OK, since we have a conversation going on it, here's my file and a brief description of how I do it.
-Sketch a corner rectangle that is
-->a)As tall as the part you want to make
-->b)Slightly wider than the radius you want to end up with
-Extrude to an arbitrary depth
-Create your boundary geometry. Here's it's just a plane, but it can be a surface of any description
-Sketch the profile of your "fin" to be revolved. It is a weird one this because if you want to have a "cone" shape you need this cut to have a draft and you need to account for that
-Extrude up to that boundary
-Pattern as per my video on the top of this thread, i.e. uncheck "Pattern Geometry"
-Delete the 5 faces of the resulting solid so you're left with a surface model with the front face and the "notches" you made to it
-Sketch on that front face and project the face in
-Sketch and extrude a cylinder. This can be slightly more than the radius you want to end up with. Playing around with this can give various different geometries.
-Revolved cut the sketch and you're there.
Changing the parameters of the plane results in a correct update. Angle, position, etc. And although changing the parameters of the plane, changes the cuts, if you change the parameters of the cut or the number of instances, the sketch throws an error.
I have noticed errors in face projections in other occasions in Alibre and I try to project edges instead of faces, but how would you get around this one? Let's see if the community can get me out of this bind!
P.S. Let me note that this particular geometry can be made with a revolution and parametric cuts. But you can create a boundary that is sinusoidal, as per the video Joseph made with the Foam, and create a very elaborate revolution.