I believe another method would be extract the ISO image, replace the files, recompile and load, that way you don't have to use Gecko.
Custom Desktop -
CPU: Intel Core i5 3570 3.4 GHz to 3.8 GHz (Turbo Boost)
GPU: MSI nVidia GTX 660 2 GB GDDR5
RAM: 8192MB DDR3 SDRAM PC2 10600 1333MHz
OS: Windows 7 Professional 64-bit
HDD: 1 TB Western Digital 7200RPM HDD
CPU: Intel Core i5 3570 3.4 GHz to 3.8 GHz (Turbo Boost)
GPU: MSI nVidia GTX 660 2 GB GDDR5
RAM: 8192MB DDR3 SDRAM PC2 10600 1333MHz
OS: Windows 7 Professional 64-bit
HDD: 1 TB Western Digital 7200RPM HDD
