Unable to turn off doublescan and force 320x200 core output resolution for Tandy graphics, EGA or CGA

[biffrapper]

Perhaps I don't know how and someone could kindly point me in the right direction, but I tried all the traditional methods available in DOSBox.conf, and they do not work. When I check the output from the core within Retroarch it always remains at 640x400.

See, the issue I am having is I am properly trying to emulate the Tandy CM-5 RGB color monitor through shaders, which has a much higher dot pitch(really poor, actually), so gaps between the pixels are essential to truly capture the grainy features of the tube, which enhance how games of the era looked.

It would be nice if we had a feature that would allow us to disable doublescan or even force the output resolution we are trying to achieve, so we can inject into the shader stack the lower resolution and go from there. Prompt text in particular does not look right when doublescanned to a higher resolution.

[biffrapper]

After further experimentation, away for a year, I realize that once a game starts the core switches output to 320x200, however at the prompt it forces 640x_400_. In VGA/EGA this is fine, but for Tandy modes, the prompt needs to be 640x200, as was on original hardware to display on composite and RGB monitors properly.