The reason why you are having issues is the system partition size, right now you have the engineering bootloader for the g2, which is good but you can't flash sense ROMs. If you want to use many of the recent ROMs or any sense ones really you need the eng DZhboot.
Check that main link again that I sent you and see the link for fastboot (How to why to) in there you will see instructions how to flash the dzhboot and if you want there is a PC10IMG.zip I made in post 30 of that thread that can also work.
Bear in mind that you will need to flash a new ROM after this as flashing a new bootloader will wipe system
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