Bogdan,
What you need is already made and cheap. Check out http://www.tempoproducts.com/belowtank.html
These are the same type of tanks that greasel.com, etc. sell with the heating coil mounted/installed. They are polyethelene, designed for fuel use, can be fitted with senders for gauges and have quite a wide selection. I would suggest a thin, long tank that fits up against the factory tank for minimum loss of trunk space and the spare stays where it belongs. RT

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