Thanks again Sarah. I've been aware of the German MRA range of quality screens for some years, but don't believe their Scrambler-specific Touring Windshield was available when I bought my Dart. While the MRA windshield looks like an excellent bit of kit, I think I will stick with my Dart for the time being.
I mostly do short rides of around 100 to 300 kms on country roads, and as the seasons here are beginning to warm-up, the Dart will be fine. I only thought about the need for maybe improving wind protection because I have a 3 day/1500 km trip coming up in late October. However, as my plan is to avoid boring motorways I should be ok - looking forward to it.