I appreciate those inputs, but they do not address my concern.
I do understand that *I* can just make changes in the FTM tree, and if there are never any changes in the online version, it will never sync 'downward' because it has no changes.
BUT, we have seen major ills with the syncing business; therefore, I do not wish to chance that a glitch on the ancestry side makes it think that the online tree has changed, and sync a corrupted tree/media down into my computer version. I just don't trust everything to always work right with ancestry sync; there are too many horror stories.
I should have asked more clearly...is there an option to tell ancestry to only do it in the upward direction? I am gathering the answer is no, or someone would have said that.