Butters yes this should work. Once you import the .spa archive file then go to page settings and where it says channel say 1-10 just below that you can offset channels. Say from 20-30. Try that and let me know. Just hope it works for stuff programmed before the offset. That I have not tested. Let me know how it works please. Also save a back up copy invade this doesn't work or you make a error.
Sincerely,