Comments:
1, I found clear pipe not worth the extra cost. They get dirty with algae if you don't keep the light out.
2, that cylinder tank looks nice. Wish I can afford one, but I would not like the distortion due to the curved surface.
3, for the half-hex tank, I don't feel comfortable with silicone for the acrylic panels. I would also bend the front instead of making it out of 5 separate panels. It is very difficult to cement (I know you say silicon) the angled edge.
4, the diagram for the easy as pie is very confusing. I figure that it is a sump with top and bottom baffles (diagrams on the right side) and the one on the left seem to show that there is a PVC pipe right on top of the baffle... why? The two diagram in the middle are top and side view. Am I right?