2. At the risk of biasing the replies, my first thought is to install High Sierra, make several clones, and then test DW 5.0 on one of the clones. Or, is that too fraught with peril?
I'll guess that attempting to run an outdated version of DW on a clone won't be perilous, but neither would I have any faith in the results it returns if it runs.
The new Great Equalizer is the SEND button.
In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire
