Hi Troels, I would highly recommend you create a system test for the new functionality in this branch. How would you suggest that this is implemented in the front end? Would this be a new option for the relax_disp.plot_disp_curves user function, to choose between offsets or CPMG frequencies? It would be good if this is discussed and properly designed on the mailing list. Then either the current tests could be modified or a new one added which implements the ideas. Once the tests pass, then we will know that the code is fully functional. It would be good if a test somewhere actually checks the contents of these Grace files as well, just so we know that the code will work perfectly forever into the future. Cheers, Edward