have lil 15 ft aluminum rexcraft that im rebuilding using an old 72 40 hpmotor been told its a gas guzzler need input on gastank are plastic better then metal am being told get 2- 6 gal containers in rear would like to take advantage of covered front empty space and have custom built gastank to gas up thru top of boat however beentold i need to balance weight any advise yall thanks a mil aka texsguns