Included with my "kit" was a plastic seat. It was intended to be used as the forward seat. The original kit had a very different seat made from composites. The plastic seat that I received was too wide to fit in the lower areas of the fuselage, so I needed to come up with a replacement.
The first thing I did was to try and figure out sizes, angles and locations. I built a mockup out of wood to get the basic layout. Here you see it in the fuselage.