First things first, the material needs to be cut roughly the correct size. There is quit a bit of shrinking to be done and any extra material will only hinder the process. I used some thin paper to make a rough template. Everywhere there is a fold, the metal will be required to be shrunk.
Transferring it to some aluminum sheet, I marked the area that I did not want to manipulate. This area will be the relatively flat sides of the tank.
I use a set of thumbnail shrinking dies in my Pullmax. There are some disadvantages of using a Pullmax to shrink with compared to using a power hammer. Mainly, the Pullmax doesn't compensate for the change in material thickness. A power hammer has a spring loaded anvil and tends to be much less abrupt. As I have not gotten very far on my power hammer build, so this is really my only option.
After a slight adjustment on the die spacing, I have the basic shaped roughed out. You can see my markings where the front needs to be brought out or raised "up". It appears that I actually shrunk it a bit too much, however, the English wheel will have no problem stretching it back out.
I am always amazed at how well the English Wheel smooths out the lumpy mess left from the shrinking dies. This is only after a couple minutes of wheeling.
There is still a way to go, but at least the hard part is done.
Here is the other tank that I built:
