The roundel stencils are a right fiddle on the double curvature of a tank. I went with 1" digits on the Big 4 and 1 1/4" on the RE. Both bikes have a 3" roundel but 4" might be nice if you have room.
There is nothing on the primary chaincase side of the fuel tank I'm afraid. There are photos of the tank posted on the WD16H & Big 4 website if you are interested.