Here is a litte sample that I drew in Blender to visualize what I am planing to create:
I already have the code to generate the cone and the spheres as mentioned in my former Post Combine 3D objects in XNA 4.
I thought that it would be nicer to generate a model and add these models to the sceen graph. My problem for now is that I wasn't able to generate a model out of my primitivas. I was planning to create one Mesh for the cone and one for each sphere that I want to attach to the cone and arrange all this in a Model, but there are no constructors for a Model or a Mesh.
So the question is: Is there a way to generate a model out of my primitives?