Curvature

 

The leather is on. Looking smart.

Not the easiest thing to measure as it's all very curvy. 

The easiest thing to do was to cover the frame ridge with masking tape then use a pencil to take a rubbing of the shape. The masking tape then peels off and can be stuck to the leather and cut out. As luck would have it, we have a small metal ruler which is exactly the same width as the ridge, so that was handy as a guide. 

 

 

 Et voila!