For all JTAGgers, this is what I did and it should work. (Won't know until I've played more of the game)
(You will need just over 25GB of free space on your PC to perform this operation. Or 12.5GB if you do
1 disc at a time)
1) Using xbox backup creator 2.9, extract files from cpx-ds2a.iso(disk 1) to a folder "Dead Space 2"
2) Delete $SystemUpdate folder
3) Rename bigfile0.viv to bigfile0_0.viv and bigfile1.viv to bigfile1_0.viv
4) Extract files from cpx-ds2b.iso (you only need bigfile0.viv and bigfile1.viv ) to "Dead Space 2"
5) Rename bigfile0.viv to bigfile0_1.viv and bigfile1.viv to bigfile1_1.viv
Then use binary copy in command prompt (in linux dd should do the trick) to combine bigfiles from dvd1 and dvd2 to one bigfile:
6) Open command prompt and navigate to the to "Dead Space 2" folder. (hold shift > right click > open command window here)
7) Command: copy /b bigfile0_0.viv + bigfile0_1.viv bigfile0.viv /b
8) Wait while file is created.
9) Command: copy /b bigfile1_0.viv + bigfile1_1.viv bigfile1.viv /b
10) Wait while file is created.
11) Delete bigfile0_0.viv, bigfile0_1.viv, bigfile1_0.viv and bigfile1_1.viv
12) Upload "Dead Space 2" to your JTAG
13) For inturnal HDD users, create a QuickBoot file, so you can launch the game from the dash
If you want to store it with your other GoD's, place the files from "Dead Space 2" into 454108df\00007000
So the final folder structure on your JTAG will be...
/Hdd1/Content/0000000000000000/454108df/00007000/bigfile0.viv, bigfile1.viv, blah blah blah
Thanks to DarkNRG @ TL for most of the info