Tips for modeling Metropol Parasol form

I am working on a design for a bench that mimics the form of the Metropol Parasol in Seville, Spain. It is going to have the same overall shape from the above view, with the columns as the legs, but the top will be flat instead of contoured. I am having trouble modeling the fluid connections between the columns and the top slab. I have tried a few different methods (loft, blend, sweep) but the connections between the forms are not coming out as organic as I intend.

I tried using the grasshopper file used in this thread
But my model still did not come out smoothly like in their images.

Here are my Rhino and GH files
Metropol Parasol (12.3 KB)
Metropol Parasol Bench.3dm (1011.8 KB)

If anyone has ideas on steps I could take to model this differently, or explanations on why my Grasshopper file is not working, I would appreciate it a lot! Also, if anyone knows where I could download a free 3D model of it, that would be very helpful as well.