Float From 2 Dished Ends

We would like a float that moves through the water easily, has a soft/gentle response to waves, is strong and durable, and yet not expensive. One possible solution is two aluminum dished ends. There are presses that make dished ends in a few hours. also here. If we combine two of dished ends we can have a shape sort of like a flying saucer. If we turn it on its side and put it halfway down in the water then the part under the water is similar to a boat shape.

I want a "dished only" shape, no flang or knuckle. I want a diameter of 9.5 feet and a height of 1.5 feet. So two of these welded to gether would be 9.5 feet diameter and 3 foot thick. I think 1 cm thick marine aluminum would be good. I want 3 attachment points that are connected on both sides and for chains to connect to.