I'm not sure if this helps you, but Sim City (J) is the ROM most suggest as the donor in an ARM7 fix. I am hearing at another site (which I can't mention here) that Juiced 2 isn't working on most people's flashcarts. In fact, at the point when I read the post, only the R4 was reported as working with the Juiced 2.
I just put Juiced 2 on my R4....runs great. I didn't need to ARM patch it at all, just trimmed it with NDSTokyoTrim 0.50. Trimmed to about 25megs. Looks like it's running at 60fps. Graphics look pretty detailed for a DS game. So far the sense of speed isn't all that, but I just started playing it and the early cars ARE slow, like less than 100mph slow. Hopefully the sense of speed will get better as I progress through the game and get faster cars. Control seems pretty tight so far and I'm kinda diggin' the music on it too. Kind of a techno-rock sort of music.
The biggest complaint so far is that it seems to have to do the "loading" and "saving to card" thing all the time. It's not too extreme, but sometimes it sits there for about 2-5 seconds saying "loading" or "saving to card" even when you cancel a race in the middle. And it does it for nearly every transition between race and menus. I consider that a minor inconvenience though as I generally like racing games....especially ones of the non-cutesy variety.
Anyway, hope you get 'em going. Both games are worth a look. I was rather surprised with DK Jungle Climber.