Hi all. I wish to update MacBookPro from Yosemite 10.10.5 to either Sierra or High Sierra. My great concern is: how would behave the Keynote slides created with Keynote 6.6.1 (Yosemite) once I open them with Keynote 7.3.1 on Sierra or High Sierra? Would I get the slides formatted differently, probably messed-up with spaces between sentences and objects not corresponding to the original made in version 6.6.1? I have an enormous quantity of Keynote slides (I am a consultant) and I cannot afford to find all of them messed up, when opened with a newer Keynote. And I now wish to upgrade my OS due to security reason. Thanks a lot for any help, greetings from Italy.