Yay! I finally got a flawless Squirtle in Emerald! I had been trying the whole afternoon, and now I'm a bit tired, hehe.
Question time!
Will it be possible to one day determine if the Pokémon that hatches from an egg in a Third Gen game changes its nature upon evolving in a Fourth Gen game?
Not without looking at the Emerald game data, though. All you can do for now is clone the Pokemon and Pal Park it over.
Also, has a reliable way of checking your seed in HGSS been found? Which one is the easiest way to advance the RNG there? That's the only thing that's stopping me from trying to get a flawless Suicune, Latias, and Ho-Oh in my SoulSilver cart.
What kind of natures are you looking for on those?
I've RNG'd a few legends on HGSS, and the technique basically boils down to:
1) Use Emloop to hit a seed that gets you the Pokemon with few frame advancements.
2) Use a Synchronizer to boost the number of Method K frames that get you your target.
3) Talk to your Pokemon\use the radio to advance the RNG, and hope you land on one of those Method K frames. You will probably land on the correct seed a couple times and end up missing the frame.
Obviously this won't work for the roamers. But, if you're willing to settle for 31\14\31\31\31\31 Timid, seed 10B042F has one on Method K frames 3, 5, 7, 11, and 13. It's Method 1 frame 14, so you shouldn't have much problem with hitting it for Latias.