Not sure. I used a Diablo i-1000 to load the SLP canned tune when I got my SC on, then read that tune and saved it with HPT and modified it from there to what I have.
I would think you could save your current tune in the DS as the 'stock' file, modify it and reload what you want. If you don't have a wideband O2 though, you will be guessing on your mixture. Don't trust the narrowbands for tuning.
Another 1 of 371 '12 T3 LS3 M6's built.