Shallow Head Design.

Blurp...

http://dishedheads.com.au/documents/1601-Head-Types

http://www.conrexsteel.com/calculator.php

You don't.

By following the approved design procedures for the same at the facility where the design is to take place. Isn't it obvious? Anything else exposes one to the prospect of professional indemnity claims!

The other thing is that the vessel design will require review and approval from some body representing the indurance company that is to provide loss and/or burst liability indemnity insurance. So if the design is not up to scratch, one can expect that body to reject it. If the design is acceptable, there will still need to be a witness test for insurance purposes before the vessel is brought into service, so there are checks and balances along that route.

All this stuff will be/needs to be in the facility's approved design procedures. Anything else and one is on one's own as far as liability is concerned and no responsible Engineer would chose to be in such an exposed position.

You should enroll in a mechanical engineering school.

All 4 of your questions here demonstrate a complete lack of knowledge of the subjects.

As Tornado said, "You don't".