Haven't used a duox2 at all, but the X2CL is twice the size of the older X2 BIOSes. 512K rather than 256K. So that "half way" might not be a coincidence. Does the duox2 support 512K? Do you need to change any switches/jumpers to do so? How are you building the bin file you are flashing? Have you tried FlashX for BIOS flashing rather than EvoX?
-Whoopin'