Formula of calculation:
sum(a9,a10,a11,a12,b9) / 5
4a1 contains suspension points that are excluded from the average:
a13,a14,c13,c14
Exclusions usually occur if suspension points are part of the stabilo but not attached to a dedicated stabilo
main line. In other cases they might be excluded due to their function as stabilizer in case of a large front collapse.