Finally! I managed to write an initial script for wrist center position calculation based on Inverse Kinematics Geometric approach. The script has been updated to the Github repo. The wrist center calculation is considered similar to a RRP Spherical case. The case is quite simple since not theta1 is required and theta2 and d3 values will depend when a practical case with some back measurements are done. This is an initial script with most definitely some big errors. So I will be work on it later to correct it.