RubyBox and my custom mappercsa.txt file work fine with the latest DOSBox and my N800, remapped keys and all (Ctrl, Shift, Alt, etc.)! The trick was to copy the file directory '/usr/share/dosbox' from the prior DOSBox version back to internal memory. The install of the latest DOSBox erased this directory, and it seems that something in that directory is needed for the remapping to work correctly. A zip file that has the contents of that directory from my tablet can be downloaded from here.