I find ribstructure work among one of the most challenging in restoration procedures.
In this instance, the whole of the ribstructure and back had twisted quite badly but the main problem was, that the front had been pulled down in the C’s, distorting the arching of the central area of the front which didn’t just affect the look of it but had quite a negative impact on the sound.
This could have resulted from previous restoration work but was unusually severe.
The flatness of the ribstructure’s gluing surface in the Cs is very important, as a dip in that area can result in the front being pulled down and the arching and f-holes being distorted.
To increase the rib height, I usually use solid maple strips bent with a bending iron which cover both the rib and lining.