@had
Without modifying any files you can
- select "tools" > "external sd.msh" > "remount sd rw.sh", before you launch KOReader.
If you are willing to modify a file, you could do your changes to
- /adds/kbmenu/onstart/start_koreader.sh
or to
- (/mnt/onboard/).adds/koreader/koreader.sh
If I remember correctly, Ken has posted his modified script somewhere in the KSM 7 thread.