FWIW, I have discovered that if I go into Ubuntu–>Settings–>Displays and change the Primary Display from #1 to #2 (my external monitor) DT will resize itself to fit my external monitor 1280 x 1024. With this Display setting, I can slide DT from the external monitor to the laptop monitor (1600 x 900) and it still resizes to fit that display as well. For now, I will be using this setting whenever I want to use DT. I prefer the external monitor because I feel it has more accurate colors than my laptop.
Caruso