I am not the most knowledgeable chap on steam loco design, I'm afraid, but I took inspiration from a charming little Kerr- Stewart loco called sgt. Murphy, on the teifi valley line in west Wales. She had two bunkers like my model, but one side bunker would be unusual,I guess for weight distribution reasons. Most Tank locos seem to have bunkers forward (Kitson, for example), or aft ( GWR pannier) but these are usually central to the chassis members.
I'm afraid that the technical nitty- gritty, is going to be down to far more knowledgeable folk than myself.
In Rust, I Trust.