You can dump bios with a tool under windows like "Radeon BIOS editor" from techpowerup.com.
I submited new kexts yesterday with better framebuffer edit, so at first try with them without moding plists.
I'd like to see your dump before I drive you to edit your plists. But you can try to replace in both kexts :
But I bet that we have some differences in Connectors Configuration. My GPU is from Club 3D