Just burned the DVD9 copy of Smash Bros. Brawl USA onto a DVD5, and I can confirm that it works just like the DVD5 release of the Japanese Brawl.
For those of you with Wiis that have issues reading dual-layer disks (one of mine can, one of mine can't), if you'd like to do this yourself, just get your dirty paws on the DVD9 iso and open it in IMGBurn. Insert your DVD5 of choice and initiate the burning process. Chose to continue when it reminds you that there won't be enough space on the selected destination media, and burn away. The burn will fail at 55% with errors saying the destination media can't fit the rest of the data and tell it to cancel the burn. It will then ask you if you would like to attempt to finalize the disk, and hit yes, because otherwise I would assume the burn will not work.
As I was typing this, my DVD5 version was idling and during the instructional video or the "how to play" video, it froze and gave an error right after Mario smashed Bowser. Don't know if the same happens with the Japanese version because I never let it get that far. But I did successfully play a versus match, so I know the game works.
Update: Apparantly you can use the program WiiScrubber found here on GBAtemp to "scrub" the disk and it will output a DVD5 iso for you, wiiscrubbed as well. This is due to the Wii scrubber not having dual-layer support, so it will just output a 4.7 gb iso. So there's another way to make the DVD9 SSBB fit on a DVD5, but to me it seems easier to just burn the DVD9 onto a DVD5 as Wiiscrubber will probably take some time to output the DVD5 iso for you.
For those of you with Wiis that have issues reading dual-layer disks (one of mine can, one of mine can't), if you'd like to do this yourself, just get your dirty paws on the DVD9 iso and open it in IMGBurn. Insert your DVD5 of choice and initiate the burning process. Chose to continue when it reminds you that there won't be enough space on the selected destination media, and burn away. The burn will fail at 55% with errors saying the destination media can't fit the rest of the data and tell it to cancel the burn. It will then ask you if you would like to attempt to finalize the disk, and hit yes, because otherwise I would assume the burn will not work.
As I was typing this, my DVD5 version was idling and during the instructional video or the "how to play" video, it froze and gave an error right after Mario smashed Bowser. Don't know if the same happens with the Japanese version because I never let it get that far. But I did successfully play a versus match, so I know the game works.
Update: Apparantly you can use the program WiiScrubber found here on GBAtemp to "scrub" the disk and it will output a DVD5 iso for you, wiiscrubbed as well. This is due to the Wii scrubber not having dual-layer support, so it will just output a 4.7 gb iso. So there's another way to make the DVD9 SSBB fit on a DVD5, but to me it seems easier to just burn the DVD9 onto a DVD5 as Wiiscrubber will probably take some time to output the DVD5 iso for you.