I dont know if you are still developing pigeos? One wish from me would be to add an option to boot to dos prompt in DOSBox directly, if possible?
I had an issue with the graphics driver in my pi and the 7 inch screen and the 800x480 resolution. It is impossible to edit the geos.ini to resolve the issue as geos.ini is embedded in the hdd-img file. However, I managed to resolve it by adding a monitor that supported the default 1024x768 and the wanted 800x480, so everything works now at viable speed.
As a sidenote, I prefer to have a folder mapped as a drive, as this folder is accessable in unix (pi os) and as a drive in DOSBox. I understand that there is advantages to have a image file to avoid file corruption. Just my point of view