Oh course Hachille is over there, light-years ahead of everyone else. Thank you, once again for doing the thing I thought of doing (3D modeling the tank) long before I even thought of it

My S1's tank actually had the filler bent intentionally bent outwards even further than the slight slope shown, denting in the tank near the top, but it seemed to line up perfectly to the filler inlet on the body so I left that as-is. Will grab a picture when it comes down off the shelf, no idea if that's a factory tweak or not.