Effectively, the system reboots into DS mode when booting a GBA game. The hurdle is to do this while keeping the emunand knowing that the game is actually loading...thus far, no one's been able to achieve this in any sort of emunand (NTR, rxTools, palentine, MT, or gateway). Of course, there's a little more to this, but this is more or less the short of it. If this was a trivial thing to sort out, I'm sure someone (even outside of gateway) would have figured it out. I know there was some talk of getting this up and running in rxTools (at least that's what I believe I recall reading anyways), but this hasn't happened yet.