Can't help much here other than being a cheerleader of sorts, but I can confirm that DVD Decrypter also detects that same size for GT4 USA:Originally Posted by Krevnik
(From my original US copy)
Size: 5,314,478,080 bytes
But I would also caution against using this particular game as a benchmark for your application, due to some nasty protection it has (a working backup solution has not yet been found and it's been out well over two months in Japan.) I don't think anyone has even successfully decrypted the files yet that we know of, and for all we know it could have a spoofed TOC (polyphony had said a while back the game would be 9+ gigs but maybe they were blowing smoke.)
Anyway, probably something like Xenosaga EP1 or Champions of Norrath would be better test subjects... but of COURSE, we'd also like to see what could be done with GT4. A lot of us legitimate owners of the game would love to run it off HDL, especially since they ditched online anyway (LAN games through KAI will still work!)
Keep up the good work.