I haven't used NXE2GOD yet, still have to re-flash my JTAG console. But when I used NXE to install games on my other console before it got banned, it didn't install to the full 6.7GB every time like you say it is.
See:
http://stripesonfire.com/nsc/ for a list of games sizes. It seems Raiden IV is 3.4GB.
Anyway, I'm wondering how (if at all) this handles multi-disc games.
When I buy Mass Effect 2 next week, can I install both discs this way and switch between them somehow, or will I have to use the disc for this one game?