Hi! I have a Satellite C855 with the latest BIOS v6.80. There is a mod for this BIOS already but that one only includes another Advanced tab, so the option for Boot Mode is still hidden. I know that it is possible to change it, I tried changing the default setup settings by tweaking the .fd file but it seems like that is not enough. The BIOS shows up as UEFI Compatible in Windows. The BIOS is InsydeH2O Revision 3.7. The advanced mod has also an IFR file where at the value 0x79 is the Boot Menu option that is set to CSM instead of UEFI. The original .fd is the bios with only the setup defaults modified. Modify whichever you find easier, preferably the one with the advanced menus activated. I am willing to pay/donate to the person who is able to tweak this to UEFI Boot Mode. Thanks for everything, I attached the link below with the necessary files.