Parametric Bamboo Structure help

Hey Guys and Girls,

I am fairly new to the world of grasshopper so just bare with me. I have been working on a parametric tower for a while now and I have gotten quite far!! But I am now stuck on the next step, I am trying to edit the model using the plane surfaces...to make the model more dynamic, in a way to trying to achieve an hour glass type movement to the structure...at present the structure is just vertical! 

Thank you for reading and for your suggestions...and will hopefully hear from you soon

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