Sketch for the mail wagon

I'm planning a basic box cabin with trimmed details, a hinged front window, and sliding side doors. I started by drawing a quick sketch based on a simplistic vintage kit, then refining from there using measurements for average seat height, the seated height of my artist model and general proportions from the various mail wagon examples I've reviewed. As I've been building behind the scenes, I've already strayed from this a little, but it was a good way to visualize the basics before diving into the actual building of it.