Re: aluminum fuel tanks
Kukla, If you use the boat in fresh water, the aluminum tank can be installed pretty much anyway, that allows any water to drain from under the tank. The airspace requirement is not important. If you boat in salt water, the alunimum tank will last a long time 20+ years, as long as the tank has drainage for accumulated water.
Why not buy a plastic tank? They are cheaper, have less condensation and last forever.