, thank you for your answer.
1) Got it.
2) I'm sorry but I think I didn't understand. I scoped a perfect horizontal surface, not an inclined one. I tried to probe the reaction force on bot vertical edges like you say, but the horizontal component of the force didn't cancels out. Maybe what are you saying is that I'm interested only in vertical component of the force since, for symmetry, the horizontal component cancels? All I want from my model is the true vertical reaction force of the symmetric 3D case.
Applying the mathematical model to my project I find that the significative force is the vertical component, since with this component the theoretical calculations seem to agree, namely, the horizontal component cancels when I integrate over 360 degrees. Do you agree? Is this what were you saying?
3) Sphere of influence + growth rate seems good.
4) Thank you for the link.
I attach my project so maybe my doubts are more clear.