Hi Michael
I have also made tanks by wrapping paper around to generate the main shapes. Another alternative is to unsolder the existing tank and then use each individual part, bases, oil and petrol separation wall, petrol surge baffles, front panel, radiussed reinforcements and main top and sides flattened out as accurate patterns. It is advisable to take some photos and measurements beforehand as well to ensure that you get the side radiuses in the correct place. There is nothing to lose in this procedure as you have to completely strip the tank anyway to recover the suspension castings, the filler necks, oil pump body, drain and petrol taps for use in the new tank. Chris.