X and Fluxbox :: 800x600 as default

how can I start with 800x600 without backing up .xserverrc?

Startup with "dsl xsetup", or remaster.

no xsetup, plz.
But how to remaster? Where to change the default 1024x768?
The problem in backing up .xserverrc is that I lose the mouse autorecognition.

original here.