The basic shape of my instruments is determined by my beliefs about the physics of guitar tops. This picture shows the difference in size between the Jumbo version on the right and the Parlour version on the left.
The shape is the same, but the Parlour has been reduced to 87% of the Jumbo for a much more compact body. The scale length of the the Parlour is only 24″, compared to the Jumbo at 25 11/32″ (a standard scale length for a steel string guitar).
This means that the Parlour operates at about 88% of the string tension of the bigger instrument for the same string gauge (65.5kg wt compared to 58.0kg wt). So as well as being more compact, the touch of the smaller guitar is softer. My thinking originally was to build a guitar for people who wanted to make an easier transition from nylon to steel strings.
What I discovered about the Parlour is that it lost very little to the Jumbo in its volume and projection.