[CentOS] How to correct LiveKDE stick?

Sat Jan 9 12:10:11 UTC 2016
Timothy Murphy <gayleard at eircom.net>

CentOS-7-x86_64-LiveKDE-1511.iso crashes
on my AMD/ATI Radeon machine.
I installed CentOS-7.2 by first installing
CentOS-7-x86_64-LiveKDE-1503.iso, then appending 
to /etc/default/grub and running update-grub.

My question is: would there be any way,
short of re-compiling the ISO,
of altering the grub.cfg seen when booting from a USB stick?

Timothy Murphy  
gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin