I just read that the new version of the linux Catalyst drivers, the 1.6, lets you overdrive the cards over the bios limits. I dont know if they are included already in Linuxcoin, but if they are not it would be a nice addition since it removes the need to flash the bios of the cards.
EDIT: For reference:
http://forum.bitcoin.org/index.php?topic=19776.msg258398#msg258398Thanks for the info

A risky one !! Most if the hardware testing had been done with 11.4 I'm testing 11.6 as we speak

if I think it's stable enough I'll add it as an option via the package manager.
I dont know if you are done with this, but it seems to be a false rumor. I just tested it in my XFX and the 11.6 drivers do NOT allow me to go beyond the bios limits.