PVC Rack Riser

I created this riser so that I could expand how I use my work truck rack. The bottom of the print is so that it can be mounted quite nicely on top of two 6" schedule 40 pvc pipes. The top is so that a 4" schedule 40 pvc pipe can be mounted to the top of the model.This is my first design and it is exported as ‘low quality’ so it is not as refined as I'd like.