Just erase the 1st version and start over. If you saved the mapping file you can load the mapping file, make changes, save the mapping file with a new name or the same name (and overwrite). I have often saved the mapping file with different names, because sometimes the 1st version still came out better than subsquent tries. And I still like to delete the first xseq otherwise effects can be merged in ways I did not understand or anticipate. You can even open an existing xseq and import just another prop that you did not do the first time.
