Generic CADD can run full screen and, on a wide-screen monitor, Generic CADD can run without distortion even though it was designed for conventional CRT monitors (aspect ratio 4:3). First set the DOSBox configuration file for fullscreen:
Then set Generic CADD to run in video mode 106h with the VESA16.vgd driver or 107h with the VESA256.vgd driver (or to a lower resolution, if necessary). Generic CADD has a command -- RA -- to adjust for the screen aspect ratio. When you execute the command, two lines are shown on the screen and you you enter the measured lengths of the lines (nominally the width and height of the screen) or you can enter the screen aspect ratio, e.g. "8 5". This will adjust Generic CADD so that circles are round and squares, square.
If the RA command doesn't exist, which may be the case for Generic CADD version 6.0.0, set the ratio of the two numbers in line 72 of the environment file, "environ.fil", (normally "8.750000 6.750000") to the aspect ratio of the screen, e.g. "16.000000 9.000000."