I am able to get a full-screen disply using Ctrl-Alt-F , but only in xdosemu. I believe there is a way to set the full-screen parameter as an argument when running dosemu, but I dont use it and it is explained somewhere in the dosemu docs. Ctrl-Alt-F allowed me to run descent in full-screen in xdosmeu.
Also note that i use the dosemu & freedos binaries. If I try to compile the source using Knoppix live cd it wont work because it makes some files read-only.

Moustache