Nucleus-nucleus cross sections

The radius of the projectile particle is used during the calculation of the reaction cross section in the class G4ComponentGGNuclNuclXsc, and I find that there is a large drop about the calculation of particle radius fbetween A =48 and A=51. This has a great impact on the calculation of the cross-section,so how to deal with it ?

_Geant4 Version:_10.05.p01