From my inexperienced viewpoint, yes, running in high is ok. I've been testing the system with Diff-Lock one and off this last week and week-en and it certainly responds better in turns with Diff off. So if I'm in the woods with sharp turns, 3' of snow, I stop and turn Diff Off and it performs great. On open lakes with 12" or less of snow I run high with Diff off. On bare ice -- scary -- I run high with Diff on, but go slow as this machine can get sideways quickly.
I'm going to add a few studs for better control on hard glazy snow and bare ice.