Have them set up a dedicated 2016 test workstation (or VM). I make that a requirement of any upgrade that crosses Crystal versions. First, if both Crystal versions are present it's not really a proper test environment. Second, you don't waste time on things like this. Third, the user's first experience of the new version isn't a failure. Fourth, if they don't have a free workstation they have an incentive to get the testing done TODAY, not next month when things slow down...